Understanding ICAO
ETOD requirements
ICAO Study best GIS practice by Gilbert Lasnier
ICAO supports the implementation of ETOD (awareness, training, state implementation). Many
agencies or third-parties vendors created tools, software and other added value provide ETOD.
Table of Contents
Overview of ETOD ......................................................................................................................... 4
1.
Area 1 - Terrain and Obstacle - Coverage Areas: ............................................................... 5
Entire territory of the state ................................................................................................ 5
2.
Area 2 - Terminal Control Area: ......................................................................................... 6
TCA , TMA ...................................................................................................................... 6
ICAO 2008 terrain data and obstacle: .............................................................................. 7
3.
Area 3 - Aerodrome Area: .................................................................................................. 8
4.
Area 4 - CAT II and CAT III Operation Area: ................................................................... 9
5.
3D VIEW - SAN FRANCISCO BAY: ............................................................................. 11
6.
ETOD work flow - Coverage Areas: ................................................................................ 11
Terminology ................................................................................................................... 12
Terrain and obstacle data has been collected .................................................................. 12
7.
Regional Seminars ............................................................................................................ 17
8.
State Working Group ........................................................................................................ 17
9.
TIN-based terrain model: .................................................................................................. 20
DPS_DeliveryInformation.deliveryFormat (DPS_DeliveryFormat.specification) ........ 20
DPS_DeliveryInformation.deliveryMedium (unitsOfDelivery) ..................................... 20
DPS_DeliveryInformation.deliveryFormat (DPS_DeliveryFormat.formatName) ........ 20
DPS_DeliveryInformation.deliveryFormat (DPS_DeliveryFormat.version) ................. 20
DPS_DeliveryInformation.deliveryFormat (DPS_DeliveryFormat.specification) ........ 20
Metadata ......................................................................................................................... 20
10.
Techniques Available.................................................................................................... 21
Conventional Terrestrial Survey ..................................................................................... 21
Aerial Photogrammetry .................................................................................................. 21
Airborne Laser Scanning ................................................................................................ 22
Interferometric Synthetic Aperture Radar ...................................................................... 22
Sensor Fusion.................................................................................................................. 23
Data Processing .............................................................................................................. 23
Conventional Terrestrial Survey ..................................................................................... 23
11.
Terrain and Obstacle, Coverage Areas - AREA 3-4: .................................................... 24
Areas 1, 2 and 3. ............................................................................................................. 27
12.
Working with Lidar Data in ArcGIS 10.1 .................................................................... 28
13.
Terrain and Obstacle, Coverage Areas - Area 1: .......................................................... 28
14.
Terrain and Obstacle, Coverage Areas - Area 2: .......................................................... 29
1
15.
eTOD Sources ............................................................................................................... 31
AREA 1 - Shuttle Radar Topography Mission ............................................................... 31
AREA 2 (3 and 4) - LIDAR ........................................................................................... 31
AREA 3 and 4 - Differential GPS .................................................................................. 31
AREA 2 - Airborne IFSAR ............................................................................................ 32
i.
(Interferometric Synthetic Aperture Radar) ............................................................... 32
ii.
eTOD Software ....................................................................................................... 32
iii.
Key Features: .......................................................................................................... 32
iv.
The unique features of GDMS are: ......................................................................... 32
16.
Aerial Photogrammetry................................................................................................. 35
17.
Airborne Laser Scanning .............................................................................................. 36
18.
Interferometric Synthetic Aperture Radar .................................................................... 37
19.
Data Collection Techniques for Terrain ....................................................................... 38
20.
Terrestrial Survey.......................................................................................................... 38
21.
Airborne Laser Scanning .............................................................................................. 38
22.
Aerial Photogrammetry................................................................................................. 38
23.
Interferometric Synthetic Aperture Radar .................................................................... 39
24.
Comparison and Recommendation ............................................................................... 39
Data Collection Techniques for Obstacles .................................................................................... 41
25.
Terrestrial Survey.......................................................................................................... 41
26.
ALS ............................................................................................................................... 41
27.
Aerial Photogrammetry................................................................................................. 42
28.
IfSAR ............................................................................................................................ 42
29.
Comparison and Recommendations ............................................................................. 43
30.
Size of Data ................................................................................................................... 45
31.
New Metadata about a Feature (or Feature TimeSlice) ................................................ 46
32.
DOGAMI Lidar Viewer ................................................................................................ 47
"LiDar" SURVEYS ...................................................................................................................... 49
33.
Light Detection And Ranging ....................................................................................... 49
34.
How does it work? ........................................................................................................ 49
35.
Click here to see a video of this service ........................................................................ 50
36.
Deliverables .................................................................................................................. 50
Point Cloud ..................................................................................................................... 50
Imagery ........................................................................................................................... 53
2
Contours .......................................................................................................................... 54
DTM ............................................................................................................................... 55
37.
Uses for LiDAR Scanning ............................................................................................ 56
38.
Technical Background of LiDAR ................................................................................. 56
Technical Introduction .................................................................................................... 56
Mission Planning and Preparation .................................................................................. 56
Data Processing Workflow ............................................................................................. 57
Personnel & Equipment .................................................................................................. 57
Helicopter ....................................................................................................................... 58
Accuracy ......................................................................................................................... 58
Horizontal absolute accuracies ....................................................................................... 58
Vertical absolute accuracies ........................................................................................... 58
Our Equipment................................................................................................................ 59
Inertial Measurement Unit (IMU) .................................................................................. 59
GPS Base Stations .......................................................................................................... 60
Quality ............................................................................................................................ 61
LiDAR Penetration ......................................................................................................... 61
Aircraft safety ................................................................................................................. 61
Eye safety........................................................................................................................ 61
Safety Plan ...................................................................................................................... 62
3
OVERVIEW OF ETOD
According to the International Civil Aviation Organization's (ICAO) new requirement
(Amendment 33) in Annex 15, all ICAO participating states are to ensure the availability of
terrain and obstacle data in electronic format between November 20, 2008 and November 12,
2015. This data shall be defined by four coverage areas around any airport, collected according
to specific numerical requirements for each area, and stored in a geodatabase (dataset ICAO
terminologies) with ICAO-defined attributes for the obstacle and terrain feature classes. Obstacle
features can be represented as points, lines, or polygons, and terrain data can be added as a
raster dataset in different format (All feature classes must be modeled according to the feature
catalog in ICAO Doc 9881). Reliable and precise obstacle and terrain data for in-flight and
ground-based applications can provide significant safety benefits for international civil aviation.
Ideally the data should be presented in a geographical information format to readily permit
evaluation and presentation to users like (pixel elevation tool tip).
(Source of this modified paragraph is found on:
http://www.esri.com/library/whitepapers/pdfs/esri-aeronautical-implementing-etod.pdf )
Note: To facilitate compliance, Esri has added Electronic Terrain and Obstacle Database (eTOD)
capabilities to Esri® Aeronautical Solution.
4
1.
AREA 1 - TERRAIN AND OBSTACLE - COVERAGE AREAS:
The coverage areas for collecting and recording sets of electronic terrain and obstacle data in the
database are defined as follow Annex 15 chap:10 Elevation Terrain Modeling
Entire territory of the state
State must create and maintaining his dataset electronically compliant with ICAO publication
standards ICAO-compliant database for obstacles, airspace data input (Notam) and terrain DTM
publication (GIS platform) Some GIS technologies are designed like WEB GIS SERVER for
assuring access 24/7 from anywhere in the world Platform
Technology
Precision:
Vertical
Horizontal
Obstacle
Vertical
DTM
1m
1m
IFSAR
1m
1m
1m
Terrestrial Survey
1.0 cm
5
2.
AREA 2 - TERMINAL CONTROL AREA:
TCA , TMA
Terrain data collection:
1. “Within the area covered by a 10-km radius from the ARP, terrain data shall comply with the
Area 2 numerical requirements.
2. In the area between 10 km and the TMA boundary or 45-km radius (whichever is smaller),
data on terrain that penetrates the horizontal plane 120 m above the lowest runway elevation
shall comply with the Area 2 numerical requirements.
3. In the area between 10 km and the TMA boundary or 45-km radius (whichever is smaller),
data on terrain that does not penetrate the horizontal plane 120 m above the lowest runway
elevation shall comply with the Area 1 numerical requirements.
4. In those portions of Area 2 where flight operations are prohibited due to very high terrain or
other local restrictions and/or regulations, terrain data shall comply with the Area 1 numerical
requirements.
Note.— Terrain data numerical requirements for Areas 1 and 2 are specified in Table A8-1.
6
ICAO 2008 terrain data and obstacle:
Terminal control area per Aeronautical Information Publication (AIP) or not exceeding a 45 km
radius from the airport (ARP) (whichever is smaller) (For aerodromes without a legally defined
terminal control area, a 45 km radius applies.)
Precision:
DTM
Vertical
Horizontal
Obstacle
Vertical
Horizontal
0.1 m
0.1 m
0.1m
0.1 m
Technology
LIDAR
0.1m
0.5m
Terrestrial Survey
1.0 cm
Technology
LIDAR
0.1m
0.5m
7
3.
AREA 3 - AERODROME AREA:
At instrument flight rules (IFR) aerodromes/heliports, from runway edge to movement areas
Terrestrial Survey
1.0cm
Precision:
DTM
Vertical
Horizontal
0.01 m
0.01 m
Obstacle
Vertical
Horizontal
0.01m
0.01m
8
4.
AREA 4 - CAT II AND CAT III OPERATION AREA:
120 m wide and 900 m long area at precision approach category II and III runways
Precision:
DTM
Vertical
Horizontal
Terrestrial Survey
1.0cm
0.01 m
0.01 m
Obstacle
Vertical
Horizontal
Horizontal
0.01m
0.01 m
0.01 m
9





http://gis.icao.int/FLEXVIEWER
terminal control areas (TCA)
Traffic Management Advisor (TMA)
control zones (CTR)
military control areas (MIL CTA)
ESRI 3D REPRESENTATION AIR SPACE TO INCLUDED.
10
5.
3D VIEW - SAN FRANCISCO BAY:
ICAO has also released Doc 9881—Guidelines for Electronic Terrain
Workflow to create the coverage areas
the terrain and obstacle data has been collected for each coverage area
6.
ETOD WORK FLOW - COVERAGE AREAS:
The coverage areas for collecting and recording sets of electronic terrain and obstacle data in the
database are defined as follow Annex 15 chap:10 Elevation Terrain Modeling
Also following the Annex 14 Controlling Surfaces, OEI (Obstruction Identification Surfaces
(OIS)), NAVAID or other data sets we need to have multiple layers to visualize the relationship
of the proposed or existing obstacle with aerodrome. The data set must be compatible with the
latest Aeronautical Information Exchange Model (AIXM) XML structured format created for
Aviation data exchange compatible with all the serious GIS software around the world.
1) Terrain and obstacle data has been collected for each coverage area
2) eTOD Obstacle Area Creation—Construct each coverage area (included as subtasks)
according to the specifications in ICAO Doc 9881 and store each area in the
ObstacleArea feature class.
3) Populating Relationship Classes—Create the relationship between each obstacle feature
and its related coverage areas to populate PointObstacleArea, LineObstacleArea, and
PolygonalObstacleArea.
4) Link of this services: Online Flex application publishes the new OIS tools as Web
services and resultant layers for obstacle analysis.
11
Terminology
ICAO use terminology in ICAO SARPs use one of three verbs to indicate the status of the text:
Requirement using the operative verb ``shall`` are mandatory.
Requirement using the operative verb ``should`` are recommended.
Requirement using the operative verb ``may`` are optional.
Terrain and obstacle data has been collected
Area 1-2
Area 3-4
The coverage areas for collecting and recording sets of electronic terrain and obstacle data in the
database are defined as follow Annex 15 chap:10 Elevation Terrain Modeling
ICAO Annex 15 Text
Electronic terrain data for each area shall conform to the applicable numerical requirements in
Appendix 8, Table A8-1
Table A8-1 “Terrain data numerical requirements” :
Post spacing
Vertical
accuracy
Vertical
resolution
Horizontal
accuracy
Confidence level
Data
classification
Integrity level
Maintenance
period
Horizontal
resolution
Area 1
Area 2
Area 3
Area 4
3 arc seconds
(approx. 90 m)
30 m
1 arc second
(approx. 30 m)
3m
0.6 arc seconds
(approx. 20 m)
0.5 m
0.3 arc seconds
(approx. 9 m)
1m
1m
0.1 m
0.01 m
0.1 m
50 m
5m
0.5 m
2.5 m
90%
90%
90%
90%
Routine 1 × 10– Essential 1 × Essential 1 × Essential 1 ×
3
10–5
10–5
10–5
as required
Area 1
1m
as required
Area 2
0.1 m
as required
Area 3
0.01 m
as required
Area 4
0.01 m
12
Table A8-2 “Obstacle data numerical requirements”
Area 1
Area 2
Area 3
Vertical
accuracy
Vertical
resolution
Horizontal
accuracy
Confidence level
Data
classification
Integrity level
Maintenance
period
Area 4
30 m
3m
0.5 m
1m
1m
0.1 m
0.01 m
0.1 m
50 m
5m
0.5 m
2.5 m
90%
90%
Routine 1 × 10– Essential
3
10–5
as required
as required
1
90%
× Essential
10–5
as required
1
90%
× Essential
10–5
1
×
as required
Obstacle data elements are features that shall be represented in the data sets by points, lines,
polygons.
Area 4 terrain data Appendix 8, table A8-2 Guidance on appropriate obstacles, Aeronautical
Chart Manuel DOC 8697.
Other Information below provided from this EuroControl document:
http://www.eurocontrol.int/sites/default/files/content/documents/informationmanagement/20120305-etodguidance_-v2.pdf
High resolution data acquisition result in up to 10,000 points per 10,000 square meters (1
Hectare)
The provision of terrain and obstacle data in accordance with ISO 19100 series of standards
allow the data sets delivered to be utilised by GIS.
Standards for terrain and obstacle:
- Catalogue Service (CS)
- Web Feature Service (WFS)
- Web Map Service (WFS)
o ICAO San Francisco Bay services
o ICAO GeoEye services
- Web Coverage Service (WFS)
13
1. “Within the area covered by a 10-km radius from the ARP, terrain data shall comply with the
Area 2 numerical requirements.
2. In the area between 10 km and the TMA boundary or 45-km radius (whichever is smaller),
data on terrain that penetrates the horizontal plane 120 m above the lowest runway elevation
shall comply with the Area 2 numerical requirements.
3. In the area between 10 km and the TMA boundary or 45-km radius (whichever is smaller),
data on terrain that does not penetrate the horizontal plane 120 m above the lowest runway
elevation shall comply with the Area 1 numerical requirements.
4. In those portions of Area 2 where flight operations are prohibited due to very high terrain or
other local restrictions and/or regulations, terrain data shall comply with the Area 1 numerical
requirements.
Note.— Terrain data numerical requirements for Areas 1 and 2 are specified in Table A8-1.
http://www.icao.int/WACAF/Documents/Meetings/2011/afi_etod/docs/dp03.pdf
14
1. “Obstacle data shall be collected and recorded in accordance with the Area 2 numerical
requirements specified in Table A8-2:
a) Area 2a: a rectangular area around a runway that comprises the runway strip plus any
clearway that exists. The Area 2a obstacle collection surface shall have height of 3 m above the
nearest runway elevation measured along the runway centre line, and for those portions related
to a clearway, if one exists, at the elevation of the nearest runway end;
b) Area 2b: an area extending from the ends of Area 2a in the direction of departure, with a
length of 10 km and a splay of 15% to each side. The Area 2b collection surface has a 1.2%
15
slope extending from the ends of Area 2a at the elevation of the runway end in the direction of
departure, with a length of 10 km and a splay of 15% to each side;
c) Area 2c: an area extending outside Area 2a and Area 2b at a distance of not more than 10 km
from the boundary of Area 2a. The Area 2c collection surface has a 1.2% slope extending
outside Area 2a and Area 2b at a distance of not more than 10 km from the boundary of Area 2a.
The initial elevation of Area 2c shall be the elevation of the point of Area 2a at which it
commences; and
d) Area 2d: an area outside the Areas 2a, 2b and 2c up to a distance of 45 km from the
aerodrome reference point, or to an existing TMA boundary, whichever is nearest. The Area 2d
obstacle collection surface has a height of 100 m above ground.
2. In those portions of Area 2 where flight operations are prohibited due to very high terrain or
other local restrictions and/or regulations, obstacle data shall be collected and recorded in
accordance with the Area 1 requirements.
3. Data on every obstacle within Area 1 whose height above the ground is 100 m or higher shall
be collected and recorded in the database in accordance with the Area 1 numerical requirements
specified in Table A8-2.”
http://www.icao.int/WACAF/Documents/Meetings/2011/afi_etod/docs/dp03.pdf
Table A8-3 “Terrain attributes”
Terrain attribute
Area of coverage
Data originator identifier
Acquisition method
Post spacing
Horizontal reference system
Horizontal resolution
Horizontal accuracy
Horizontal confidence level
Horizontal position
Elevation
Elevation reference
Vertical reference system
Vertical resolution
Vertical accuracy
Vertical confidence level
Surface type
Recorded surface
Penetration level
Known variations
Integrity
Date and time stamp
Unit of measurement used
Mandatory/Optional
Mandatory
Mandatory
Mandatory
Mandatory
Mandatory
Mandatory
Mandatory
Mandatory
Mandatory
Mandatory
Mandatory
Mandatory
Mandatory
Mandatory
Mandatory
Optional
Mandatory
Optional
Optional
Mandatory
Mandatory
Mandatory
16
7.
REGIONAL SEMINARS
The awareness sessions may cover the following topics:
a) The history of terrain and obstacle data;
b) The terrain and obstacle data requirements;
c) Overview of System-wide Information Management/AIM and how terrain and obstacle
data support this;
d) The uses of terrain and obstacle data;
e) GIS and survey techniques;
f) Feature capture rules;
g) Institutional issues;
h) Data sources;
i) Responsibilities;
j) The way forward.
8.
STATE WORKING GROUP
1. The State AISP;
2. The Military AISP;
3. Civil procedure design authority;
4. Military procedure design authority;
5. The regulator;
6. The Ministry of Transport;
7. The State survey organisation;
8. The Military survey organisation;
9. The national geodetic agency;
10. Aerodrome operators;
11. Representation (probably at a national level) of local authorities or those with the
responsibility for safeguarding and/or approving construction in the vicinity of an
aerodrome;
12. Authorities or organisations responsible for the authorisation or maintenance of obstacles,
such as:
a. Broadcast transmission antennas
b. Cell phone masts;
c. Electricity transmission pylons;
d. Wind turbine farms.
e. In States, where aerodromes may be adjacent to ports, representatives of the Port
Authority.
One of the first tasks of the group could be to establish the focal points (see 4.1.5 below) in the
State.
Other tasks could include an assessment of whether the national regulation needs to change to
allow terrain and obstacle data implementation to proceed, identification of costs and
formulation of an implementation plan. This will ensure the necessary regulatory framework to
place obligations on the relevant parties.
17
“10.1.5 From 12 November 2015, at aerodromes regularly used by international civil aviation
electronic terrain and obstacle data shall be provided for:
a) Area 2a , for those obstacles that penetrate the relevant obstacle data collection surface
specified in Appendix 8;
b) penetrations of the take-off flight path area obstacle identification surfaces; and
c) penetrations of the aerodrome obstacle limitation surfaces.
Note.— Take-off flight path area obstacle identification surfaces are specified in Annex 4,
3.8.2.1. Aerodrome obstacle limitation surfaces are specified in Annex 14, Volume 1, Chapter 4.
10.1.6 Recommendation.— At aerodromes regularly used by international civil aviation,
electronic terrain and obstacle data should be provided for Areas 2b, 2c and 2d for obstacles
and terrain that penetrate the relevant obstacle data collection surface specified in Appendix 8.”
“2.3.2. Commercially available Geographic Information System (GIS), mapping and illustration
software products are obtainable internationally at a reasonable cost. Free "reader software"
which allows for viewing of charts without the need to acquire the originating software is also
widely available. In addition, the International Organization for Standardization (ISO) 19100
series of international standards for geographic information, together with related
standardization in the GIS/mapping industry, have established conditions for the interchange,
portrayal, and use of electronic chart files”.
18
19
9.
TIN-BASED TERRAIN MODEL:
TIN-based terrain model should be considered since it is more suitable than a gridded data
set.
DPS_DeliveryInformation.deliveryFormat (DPS_DeliveryFormat.specification)
Name of a subset, profile or product specification of the format.
TIFF: http://partners.adobe.com/public/developer/tiff/index.html.
TIXM: Terrain Data Model Primer, source www.eurocontrol.int / OneSky Teams.
DPS_DeliveryInformation.deliveryMedium (unitsOfDelivery)
Description of the units of delivery, such as tiles, layers, geographic areas.
File extensions: following naming convention is mandatory.
Obstacle data: .xml, metadata: .mtd.
Integrity information: crc additional file extensions must be described in a README.txt file.
Area 1: For obstacle data in Area 1, all data must be packaged in one exchange file which must
be packaged together with the metadata and the crc information in one folder.
All other areas: For obstacle data in Areas 2, 3 and 4, all data should be packaged per aerodrome
except where the outlines of different Area 2 polygons overlap. In such situations, the delivery of
Area 2 data should be organised per combined aerodrome region.
DPS_DeliveryInformation.deliveryFormat (DPS_DeliveryFormat.formatName)
Name of the data format.
AIXM for downstream data provision, simplified XML (or similar) for upstream deliveries from
data origination / surveyor.
DPS_DeliveryInformation.deliveryFormat (DPS_DeliveryFormat.version)
Version of the format.
AIXM: Version 5.1 / 2010.
(or as agreed, if deviates from AIXM).
DPS_DeliveryInformation.deliveryFormat (DPS_DeliveryFormat.specification)
Name of a subset, profile or product specification of the format.
AIXM: Aeronautical Information Exchange Model – Key Concepts – Standards, source
http://www.aixm.aero
Metadata
A profile of ISO 19115 [Reference 16] is used for terrain and obstacle data which contains all
relevant information to ensure compliance with the Commission Regulation (EU) 73/2010
[Reference 29]. The proposed metadata schema for terrain and obstacle data is based on the ISO
19115 standard [Reference 16] and AIXM 5.1. Some extensions are necessary to comply with
the requirements of ICAO Annex 15 [Reference 4].
20
Additional extensions are proposed to accommodate the metadata necessary for AIXM
conformity. As the AIXM metadata schema is also based on ISO 19115, this allows the concepts
from the AIXM metadata schema to be easily adopted.
Detailed information on metadata can be found in section 7.7 of this Manual.
10.
TECHNIQUES AVAILABLE
Conventional Terrestrial Survey
Terrestrial Survey is still the most wide-spread technique for data acquisition.
Compared to other surveying technologies, the investment in sensors and processing software for
conventional terrestrial surveying is quite low. On the other hand, the human resources needed to
perform the survey in the field are higher, when compared with any other technique.
Consequently, this method of survey, although not limited to, is usually used for localised tasks.
For the data capture of extended areas, it is often more economical to use an airborne mapping
technique. Nevertheless, airborne survey techniques are not completely independent from
terrestrial survey, e.g. benchmark surveying - the survey of highly accurate ground control
points.
Conventional terrestrial survey uses the following instruments:
- GPS receiver;
- Theodolites or Total Stations (Theodolite combined with [reflectorless]
distance measuring);
- Terrestrial positioning system (Total Station combined with a GPS receiver).
With regards to terrain and obstacle data, conventional terrestrial survey methods would be
suitable for the following tasks:
- Obstacle acquisition and maintenance;
- Terrain acquisition;
- Surveying of benchmarks for airborne mapping techniques;
- Validation of data acquired by an airborne sensor system.
Aerial Photogrammetry
Aerial Photogrammetry is a survey technique which has been used for a number of years. The
latest development in this field is mainly in regard to digital cameras and scanners. The pixel size
(either of the digital camera or the scanner) is the dominating factor in selecting the flight
parameters, to ensure that the technical requirements are fulfilled.
The most restrictive requirement for obstacle acquisition by photogrammetry is the minimum
size of the obstacles which have to be captured. To capture very thin objects (e.g. antennae, street
lamps, etc.), the image scale1 has to be bigger than with traditional survey flights. This requires a
lower flight height. With a lower flight level, the resulting spatial accuracy (x, y, z) will be much
higher than requested. Obviously, the costs for data acquisition for terrain and obstacle data are
higher than for traditional applications.
1
Image scale = flight height / focal length, e.g. camera lens with 15cm focal length and a flight height of 1,200m
above ground level will lead to an image scale of 1:8,000. With these parameters, a spatial accuracy of 15cm
vertically and 5cm horizontally can be achieved.
21
Today, analogue and digital cameras are used for photogrammetry. The only difference between
the processes, for analogue and digital cameras, is that the film of the analogue camera has to be
scanned. As soon as the images are digitally available, the process is the same for both cameras.
With regards to terrain and obstacle data, photogrammetry can be used for the following tasks:
- Terrain mapping;
- Obstacle mapping;
- Validation of ALS data.
Airborne Laser Scanning
Within the last few years, Airborne Laser Scanning (ALS), also known as Light Detection and
Ranging (LiDAR), has progressed significantly and is now a more established technique. One of
the biggest advantages of ALS, compared to conventional surveying methods, is the high-level
of automation offered through a completely digital data chain. Although ALS is a mature
technique with respect to the quality of data collection, improvements would be beneficial with
respect to data post-processing (i.e. feature detection and extraction). The more automated the
processes become, the more economical the data extraction will become.
One other significant advantage compared to conventional surveying methods is the homogenous
data acquisition over the whole area. The main drawbacks of the technique are the high
investment costs and the low number of operators that have sensors capable of obstacle mapping.
As for photogrammetry, the minimum size of the obstacle which needs to be captured is the
predominant factor for the planning of the ALS flight. If all small antennae on top of buildings
have to be captured, the flight and laser parameters have to be adjusted accordingly, to fulfil the
technical requirements.
ALS includes the following:
- Laser scanner (measures the scan angle and time of flight for each laserpulse);
- Positioning and orientation system consisting of:
- GPS receiver on the aeroplane and reference station on the ground (differential GPS
(DGPS));
- Inertial Measurement Unit (IMU) to measure roll, pitch and heading of the scanner
system.
- With regards to terrain and obstacle data, ALS methods can be used for the following
tasks:
o Terrain mapping;
o Obstacle mapping.
Interferometric Synthetic Aperture Radar
Among the different radar measuring devices, Interferometric Synthetic Aperture Radar (IfSAR)
is the most common one. IfSAR is an active sensor system using microwave (wavelength
between 2 and 100 cm) and recording the signals reflected from the terrain. Each emitted pulse
illuminates a relatively large area and the reflected signal is continuously digitised. The sampling
allows a finer resolution of the illuminated area. By repeatedly emitting pulses, each object is
illuminated several times. By combining the subsequent signals, the Doppler frequency can be
resolved which is then used to determine the location of a point with respect to its location along
the flight path and its range. By combining two spatially separated viewing positions (for which
their separation must be very accurately known), the resulting interferometric image allows the
precise measurement of the parallax of a common point in both images. This stereoscopic
22
measurement (as in photogrammetry) allows the determination of the third co-ordinate. The
workflow is very similar to aerial photogrammetry.
IfSAR systems consist of:
- Two Synthetic Aperture Radar (SAR) systems;
- Positioning and orientation system consisting of:
- GPS receiver on the aeroplane and reference station on the ground (DGPS);
- IMU to measure roll, pitch and heading of the scanner system.
With regard to terrain and obstacle data, IfSAR methods can be used for the following tasks:
- Terrain mapping2.
Sensor Fusion
Since every sensor system has its strengths and weaknesses, the combination of two sensors for
data acquisition can be considered. For terrain and obstacle data, it is expected that a
combination of a tilted ALS sensor and a digital photogrammetric camera offers many benefits in
terms of quality (completeness of data acquisition, visual validation) and efficiency (degree of
automation), for large area surveys.
Data Processing
Depending on the data collection technique, different processing steps must be applied. The
workflow for each technique is discussed in general, with particular focus on how Commission
Regulation (EU) 73/2010 [Reference 29] impacts traditional data processing (for example,
collecting metadata, data validation and documentation). This section also outlines the
transformation of data between different reference systems.
Conventional Terrestrial Survey
the typical workflow for conventional terrestrial survey. This method and the workflow shown
below have been included in this Manual as they are most suitable for obstacle acquisition in
large areas. For terrain data acquisition, the process can be simplified because GPS equipment
alone, run in Real-Time Kinematic (RTK) mode, described later in this section, is suitable for
mass data collection51.
2
There are ongoing academic research projects where IfSAR systems are used to also detect obstacles. So far, no
evidence has been provided that this data meets the quality requirements.
23
11.
TERRAIN AND OBSTACLE, COVERAGE AREAS - AREA 3-4:
ICAO GIS Aeronautical Officer Technology proposed:
1) Obstacle and other layers use Station total for 5 days 2 people survey of all control points
and obstacle, creation of data in GIS system, obstacle database and other layers (control
points, runway, navaids, vor/dme etc) add the recent raster data ( Photogrammetry or
other kind of imagery) of the aerodrome in background for Quality control, note the
precision will be 1.5cm in Horizontal and vertical more precise then the Annex 15
recommendation. Follow the Workflow of Conventional Terrestrial Survey below.
2) Terrain use GPS Mobile type RTK with a 4 wheels, collect Raw field data, input data in
GIS to create the DTM triangulation (tin function) to obtain the terrain dataset with all
the ICAO rule and recommendation. The following links are good examples to Data
collection with GPS Mobile type RTK http://www.rtklib.com/prog/manual_2.2.2.pdf and
http://trl.trimble.com/docushare/dsweb/Get/Document-270097/022543366_GNSS_Systems_BRO_0208_lr.pdf
3) In French:
ftp://ftp.trimble.com/pub/tmsupport/Survey%20controller/CD/Trimble%20Survey%20Co
ntroller/Documentation/Francais/Help/Fra_SCRTK_Survey.htm and http://www.leicageosystems.com/downloads123/zz/gps/general/brochures/GPS1200_brochure_fr.pdf
4) Read in this article in the next page from EuroControl “7.2.4.5 Comparison and
Recommendation” and “7.2.4.1 Terrestrial Survey”
5) FAA Help for surveyor https://airports-gis.faa.gov/public/surveyorsIntro.html
6) ESRI Aerodrome package http://resources.arcgis.com/fr/gallery/video//esri-aeronauticalsolution/details?entryID=143C8F19-1422-2418-8861-7E40E749FB1A
-
Photogrammetry: cost $200/km2 rural, $900/ km2 urbain
o Is the most efficient technique for data acquisition;
o The degree of automation is smaller, when compared to ALS, but the algorithms
are still evolving;
o The imagery can be used as a base for many other applications.
24
ALS: LIDAR: $350 per square kilometer data from 2012
Light Detection and Ranging (LIDAR)
Airborne Laser Scanning (ALS)
Other Lidar cost search result:
• 50-100 sq mi2:
$943/mi2 $420/km2
• PHB Montreal $300/kml2 chart type A
2 km par 10 km fois 6 for 6 runways $35000 more $3000 for traitements
•
•
•
•
•
100-150 mi2:
$704/mi2
2
150-200 mi :
$592/mi2
200-250 mi2:
$521/mi2
2
> 250 mi :
$472/mi2 $210/km2
10 km egal 400 km2 so the price is $84,000 for 400 km2 equal to zone area 2 (i the same
time 3 and 4)
• So for 84,000 for post traitement with OIS and Obstruction and other data integration for
a total of $168,000
$386-$772 per square kilometer for 1 to 2-meter postings
ALS:
- Has very high capital costs and is, therefore, less widely available;
- A DTM can be extracted almost entirely automatically. Algorithms have been
commercially available for many years (allowing separation between data acquisition and
feature extraction);
- Terrain data acquisition is performed almost at no extra cost when combined with
obstacle mapping
lidar link:
http://www.google.ca/url?sa=t&rct=j&q=lidar%20cost%20per%20km&source=web&cd=4&sqi
=2&ved=0CD4QFjAD&url=http%3A%2F%2Fopentopo.sdsc.edu%2Fshortcourses%2FGSA_20
09_Course_515%2FHaugerud%2FHaugerud3.ppt&ei=Oc5QUODjGuTu0gGv5ID4Cg&usg=AF
QjCNHjW_TPRSWfGU0zVUSuLIdyubhW8g
IfSAR: $70 per square kilometer buy by INTERMAP 2012 (NEXTMap database)
https://www1.vtrenz.net/imarkownerfiles/ownerassets/868/brochure_IFSAR.pdf
IfSAR provides the highest data acquisition rates from all currently available survey techniques.
The offered products also fulfil the quality requirements for
25
Parameter
Collection Process
Maximum Collection
Rates
Wavelengths
Maximum Operating
Speed
Ground Swath
DTM Ground Sample
Distance
DTM Vertical
Accuracy
DTM Horizontal
Accuracy
Imagery Type
Imagery Ground
Sample Distance
Imagery Horizontal
Accuracy
Representative Pricing
for Fully Edited DTMs
IFSAR / InSAR – Type
II
Collected from fixedwing aircraft at 6km to
9km in single-pass
mode.
IFSAR / InSAR – Type
I+
Collected from fixedwing aircraft at 6km to
9km in single-pass
mode.
~ 4,000km2/hr
~ 4,000km2/hr
LiDAR - Typical
Industry Values
Collected from fixedwing aircraft and
helicopter platforms at
50m to 3.5km; may
require multiple passes.
~ 200km2/hr
X-band (~3cm).
Penetrates clouds, haze,
fog, dust, light rain, and
snow.
~ 750km/hr
X-band (~3cm).
Penetrates clouds, haze,
fog, dust, light rain, and
snow.
~ 750km/hr
IR (~ 1nm). Cannot
penetrate clouds;
heavily absorbed by
water.
~ 200km/hr
5 – 9km
5.0m posting
5 – 9km
5.0m posting
0.7 to 1km
0.75 – 3.0m posting
1.0m RMSE
0.5m RMSE
0.1 – 0.5m RMSE
2.0m
1.0m
0.5 – 1.0m
orthorectified radar
imagery
~ 1.25m pixel size
orthorectified radar
imagery
~ 0.625m pixel size
intensity gray scale
image
~ 0.75 – 3.0m pixel size
2.0m RMSE
1.0m RMSE
0.5 – 1.0m RMSE
~ <$40/km2 USD
typical
~ <$40/km2 USD
typical
~ $150 – $350/km2
USD typical
26
Areas 1, 2 and 3.
http://192.206.28.84/eganp/Portals/0/Presentation/ICAO%20AFI%20ETOD%202%20April%20
2008.pdf or old http://192.206.28.84/eganp/Portals/0/Presentation/IFSAR2007.pdf
- There are only a few providers available due to the highest capital costs and proprietary
processing software of all the techniques;
- The efficiency of data acquisition is high, but is influenced by the need for marked and
surveyed corner points;
- For raw measurements, the penetration level is unclear which impacts the quality in
forested areas.
http://www.geosar.com/downloads/WhitePaper_GeospatialFramework_10-2009.pdf
IDS EXCHANGE EXPORT TO ARCINC AND EXPORT TO AIXM IMPORT ALSO AIXM
TO EXCHANGE DATA WITH JEPPESEN
AND EAD IN EUROPE OR WITH
NAVCANADA for obstacle ok BUT THE DATA OF THE ETOD orthophoto or other TIN
DTM SRTM DTM Elevation data model
https://www1.vtrenz.net/imarkownerfiles/ownerassets/868/brochure_IFSAR.pdf
LIDAR SOFTWARE PROGRAM
http://www.google.ca/url?sa=t&rct=j&q=lidar%20software%20review&source=web&cd=3&ved
=0CEMQFjAC&url=http%3A%2F%2Fwww.fsl.orst.edu%2Fsdmg%2Ffiles%2FLiDAR_USGS_
GIS_Workshop_2008_Report.doc&ei=qpQUOjpFarj0QGa2oCwAw&usg=AFQjCNFX6srK81oRAVGD8V7giaSlCVf_8Q
http://www.lidarnews.com/PDF/LiDAR_Magazine_Vol1No2_Oneil-Dunne.pdf
http://spatialis.com/products/topo/pdf/SIS_PSM_NOV2011.pdf
http://www.terrasolid.com/home.php
http://gis.mapsofworld.com/lidar/lidar-software.html
27
12.
WORKING WITH LIDAR DATA IN ARCGIS 10.1
Because of its often-massive size, lidar data can be a challenge to work with. The seminar
introduces ArcGIS 10.1 tools to quickly create a LAS dataset from a collection of LAS files,
view the data as points and TINs (triangulated irregular networks), take measurements, and edit
classification codes. You will learn how you can efficiently manage collections of LAS files
using mosaic datasets and share them to desktop and web applications.
13.
TERRAIN AND OBSTACLE, COVERAGE AREAS - AREA 1:
ICAO GIS Aeronautical Officer Technology proposed:
The coverage areas for collecting and recording sets of electronic terrain and obstacle data in the
database are defined as follow Annex 15 chap:10 Elevation Terrain Modeling
The Shuttle Radar Topography Mission (SRTM) is an international research effort that obtained
digital elevation models on a near-global scale from 56 °S to 60 °N, to generate the most
complete high-resolution digital topographic database of Earth to date. http://www.airportsuppliers.com/supplier/SLC_Geomatic_Solutions/
http://www.earthondrive.com/index.php?route=product/category&path=59_66
Terrain Data
Greater than 45 km from the ARP and Greater than 10 km from the ARP,
Survey for the DTM: I will go with IFSAR Technology for the rural zone and Urban.
Obstacle Data
I prefer to use Terrestrial Survey for Obstacle and other layers use Station total for 50 days 2
people survey or GPS Survey for all control points and obstacle, creation of data in GIS system
with excellent quality data control.
Between 10K and 45 km part of Area 2 in the Annex 15 chap:10 Elevation Terrain Modeling
If the terrain is almost horizontal;
Survey for the DTM: I will go with IFSAR Technology for the rural and Urban zone.
If the terrain is very accidently (many verticical change) ;
I will go with LIDAR Technology for the rural zone and Urban zone. In the same flight plan I
collect also with LIDAR Technology the Obstacle in the Urban zone and rural zone.
28
14.
TERRAIN AND OBSTACLE, COVERAGE AREAS - AREA 2:
The coverage areas for collecting and recording sets of electronic terrain and obstacle data in the
database are defined as follow Annex 15 chap:10 Elevation Terrain Modeling
- Terrain Data
o Survey circle of 10KM: I will go with LIDAR Technology for the rural zone
and Urban zone.
- Obstacle Data
o In the same flight plan I collect also with LIDAR Technology the Obstacle in the
Urban zone and rural zone
Maybe in the same flight plan, I make also the data collection for the Area 3 (same price).
Commercially Available Synthetic Aperture Radar Systems
System
Wavelength
Radarsat
C-band
Satellite or Supplier
airborne
Name
Satellite
MDA
ERS
C-band
Satellite
ESA
ENVISAT
C-band
Satellite
ESA
PALSAR
L-band
Satellite
JAICA
X-band
Satellite
Infoterra
TerraSARX
GeoSAR
Fugro
OrbiSAR
X- and P-band Airborne
(simultaneous
)
X- and P-band Airborne
Star3i
X-band
Intermap
Airborne
Orbisat
For Further Information
http://www.asccsa.gc.ca/eng/satellites/radarsat/overv
iew.asp
http://www.esa.int/esaEO/SEMGWH
2VQUD_ind
ex_0_m.html
http://www.esa.int/esaEO/SEMWYN
2VQUD_ind
ex_0_m.html
http://www.palsar.ersdac.or.jp/e/inde
x.shtml
http://www.infoterra.de/terrasarx.html
www.geosar.com
www.orbisat.be
www.intermap.com
29
Categorization
Candidate Data
Alignment
Layer
National
Geodetic Control
National Grid
coordinate system
/geodetic info.
National
Orthoimagery,
Orthoimagery
updated at regular
intervals
Historical
Orthoimagery
Land Features/Form Layer
National
Contours (Digital
Elevation
Elevation Models)
Dataset
Bathymetric data
National
Hydrography
Coastline (all
shorelines);
Hydrology
(streams/rivers/lakes
)
National
Transportation
Roads
Road centerline
National
Landforms/Geol
ogy
Geomorphology/soil
s
Geological base
maps
Recommended
Data Sources
Cloudy Tropics
Recommended Data Sources
Non-Cloudy
Ground survey
Ground survey
SAR/IFSAR
Aerial photography,
SAR/IFSAR
Imagery that is
available (if any)
Aerial photography
Foliage-penetrating
(P-band) IFSAR,
especially where
vegetated
Lidar, echo
sounding
Airborne or
Satellite SAR
(depending on
scale required)
Airborne or
Satellite SAR
(depending on
scale required)
Airborne or
Satellite SAR
(depending on
scale required)
Airborne or
Satellite SAR
(depending on
scale required)
Multi-frequency
SAR/ IFSAR
Lidar, IFSAR
Multi-frequency
IFSAR ;
geophysical
surveys
Lidar, echo sounding
Aerial photography,
satellite/airborne SAR,
(depending on scale required)
Aerial photography, Airborne
or Satellite SAR (depending on
scale required)
Aerial photography, Airborne
or Satellite SAR (depending on
scale required)
Aerial photography, Airborne
or Satellite SAR (depending on
scale required)
Aerial photography, Airborne
or Satellite SAR (depending on
detail)
Aerial photography, Airborne
or Satellite SAR (depending on
detail); geophysical surveys
30
Other provides for ETOD SOLUTION:
ESRI: http://www.esri.com/library/whitepapers/pdfs/esri-aeronautical-implementing-etod.pdf
AVITECH: http://eaip.avitech-ag.net/index.php?id=109
IDS: http://www.idscompany.it/page.php?f=78&id_div=5
INTERMAP
https://www1.vtrenz.net/imarkownerfiles/ownerassets/868/ADS_Prod_Overview_A4.pdf
GEOEYE: http://geoeye.com/CorpSite/assets/docs/brochures/GeoEye_AMDB_v5.pdf
AIRSERVICEUK: http://www.airservicesuk.com/eTOD_Imp.html
SLC Associates: http://www.slcassociates.co.uk/software-systems/etod-software/
JEPPESEN:
http://ww1.jeppesen.com/documents/aviation/commercial/TERR_OBSTACLES.pdf
http://ww1.jeppesen.com/industry-solutions/aviation/commercial/terrain-obstacle-database.jsp
15.
ETOD SOURCES
AREA 1 - Shuttle Radar Topography Mission
The Shuttle Radar Topography Mission (SRTM) is an international research effort that obtained
digital elevation models on a near-global scale from 56 °S to 60 °N, to generate the most
complete high-resolution digital topographic database of Earth to date.
AREA 2 (3 and 4) - LIDAR
Airborne lidar (Light Detection And Ranging) measures the height of the ground surface and
other features in large areas of landscape with a resolution and accuracy hitherto unavailable,
except through labour-intensive field survey or photogrammetry. It provides highly detailed and
accurate models of the land surface at metre and sub-metre resolution.
Lidar operates by using a pulsed laser beam which is scanned from side to side as the aircraft
flies over the survey area, measuring between 20,000 to 150,000 points per second to build an
accurate, high resolution model of the ground and the features upon it. Using LIDAR for DEM
and contour generation is faster than using conventional photogrammetic techniques and less
susceptible to data collection problems as data can be acquired during the day or night. However,
this system is weather dependent and cannot see through clouds.
AREA 3 and 4 - Differential GPS
Areas 3 and 4 also lend themselves to a ground survey mission. By mouinting a geodetic grade
DGPS Receiver on a suitable vehicle, these areas can be surveyed very quickly and at low cost.
Typically in 3 to 5 days per airport.
31
AREA 2 - Airborne IFSAR
i.
(Interferometric Synthetic Aperture Radar)
Airborne IFSAR is a fast, accurate, cost-effective source of elevation and image data. The
orthorectified imagery can provide ground-control points that can be used to link satellite or
airborne imagery to an IFSAR DEM for rectification.
ii.
eTOD Software
Much more than just a data store, GDMS is a bespoke Geospatial Information System with a
suite of tools for handling electronic terrain and obstacle data (eTOD) and carrying out
obstruction analysis against Obstacle Limitation Surfaces (Safeguarding).
GDMS enables you to maximise the benefits from your investment. With GDMS you can use
eTOD for 3D presentations, aerodrome safeguarding and management of airport development.
In common with all Geographical Information Systems, GDMS can interact with a powerful
database and create a views of the environment by creating multiple layers of information such
as raster and vector mapping, aerial and satellite images, 3d terrain data (eTOD), airports
obstacle limitation surfaces (Annex 14, Navigation Aids, etc) and User created zones. However,
unlike most GIS, GDMS can also view the data in 3 dimensions with the images draped onto the
terrain data and can carry out real-time fly through simulation.
One major difference between GDMS and other commercial GIS is that integrated into the
system is the Aerodrome Safeguarding Toolkit (AST-Pro), which carries out the automated
modeling of obstacle limitation surfaces and the analysis of obstructions. This module can
automatically create the complete Annex 14 (or CAP168) 3d model by simply inputting the
aerodrome data.
The resulting 3 dimensional model is available for use in any Workspace by simple selecting it
from the Database Manager, furthermore, the models remains completely interactive and can be
changed at any time by editing the runway criteria.
iii.
Key Features:
In addition to being a fully functional Geospatial Information System, i.e, able to import, and
display layers of information from multiple sources (geo-tiff images, dxf, shape, vector
mapping).
iv.
The unique features of GDMS are:
-
-
System can work in local grid system or WGS-84 latitude and longitude.
On screen creation of custom zones (Public Safety Zones, Restricted Airspace, etc.).
Import and storage of eTOD data along with ICAO required attributes.
QA analysis of legacy terrain data by comparison to ground truth points. Results will
predict the accuracy or the legacy data at both 1 sigma and 2 sigma confidence levels.
User can accept this result and add to the QA attributes for that particular terrain file.
Full 3d visualisation with vertical exaggeration.
Full Image draping onto terrain data.
Automated Aerodrome Surfaces modeling. (User specified parameters, e.g. Annex 14 or
other National variations such as the UK’s CAP168).
32
-
Object analysis to all visible surfaces. (typically proposed planning applications or
existing obstacles).
AIXM ready database.
Graphic screen can be split to a second screen (requires graphics card).
Output to Google Earth (obstacles and surfaces)
Technical support provided by SLC Associates, highly experienced aviation consultants
and Geospatial data experts.
Figure: Workflow of Conventional Terrestrial Survey3
3
Processes in italics indicate data in local co-ordinate system. Simplified process for terrain survey by means
of GPS-RTK in bold.
33
The following preconditions have to be fulfilled for Total Stations type survey:
- Reference station operated on points with known co-ordinates or derived by free
stationing;
- Monument control stations in a local network build the base for the terrestrial survey;
- Local co-ordinate system:
o Measurements with a theodolite are performed in a local planar coordinate system
(e.g. UTM). The heights are measured above the (quasi-)geoid, based on the
published
heights
of
the
reference
points.
Typically, such height values are labelled as MSL.
- Transformation parameters from local to WGS-84 co-ordinate system53:
o For the transformation of the surveyed points between the local coordinate system
and WGS-84, transformation parameters are needed. In order to obtain heights in
a different system (such as ellipsoidal heights or heights above EGM-96), the
local geoid must be known to a high accuracy. For a limited area, the
transformation parameters can be derived with a set of reference points, with
known 3D co-ordinates in both reference systems.
Preconditions for a GPS type survey:
- Reference station(s) for DGPS:
o The definition of measured GPS points is based on well-defined reference
stations. For the resolution of the ambiguities, at least one additional GPS station
will be used in DGPS. To improve the precision of the resulting coordinates,
measurements with short baselines are preferred. National and international
permanent GPS networks 4 , which are often operated by the national survey
agency, allow the surveyors to use more than one single, additional station to
define the reference stations with higher precision and reliability. Where
permanent or reference GPS stations transmit the correction signal by radio
waves, the receiver is capable of operating in RTK mode (Real Time Kinematic).
http://www.geod.nrcan.gc.ca/edu/rtk_f.php
Précisions planimétriques pour des vecteurs de longueurs diverses
1 km
10 km
~ 1 cm
~ 2 cm
Bifréquence
~ 2 cm
~ 4 cm
Monofréquence
30 km
~ 4 cm
Trop long
Thus, the co-ordinates of the measurement points are available without post-processing. With
GPS, the survey is performed in a world-wide geodetic system. Transformations between WGS84 and a local geodetic datum or co-ordinate system are therefore obsolete when the co-ordinates
of the reference stations are known in WGS-84.
4
An example: Online GPS Processing Service by the Australian Government http://www.ga.gov.au/bin/gps.pl.
34
16.
AERIAL PHOTOGRAMMETRY
Figure: Workflow of Aerial Photogrammetry
The following preconditions have to be fulfilled:
- Benchmarks have to be marked (signalisation) and their co-ordinates determined using
terrestrial survey;
- Flight plan based on:
o Focal length;
o Spatial accuracy requirements;
o Flight restrictions;
o Resolution requirements.
.
35
17.
AIRBORNE LASER SCANNING
Figure: Workflow of ALS
The following preconditions have to be fulfilled:
- Flight plan with:
o Flight lines;
o Scan angle;
o Scan rate;
o Pulse repetition frequency.
These parameters influence the flight height but, additionally, the flight restrictions and
topography may also impact the flight planning. The most appropriate system settings are
selected based on the topography and the technical specifications:
- Calibration flight:
o A calibration flight is performed after the mounting of the system. Periodical recalibration is recommended to compensate for drifts and changes in climate;
- Well-defined monument reference station for master GPS or provision of permanent GPS
reference network with post-processing capabilities.
The above mentioned preconditions have to be fulfilled before the ALS surveying flight is
performed. As with any airborne survey technique, it is recommended that terrestrial survey is
performed to measure specific points which are used as control points for data validation55.
These measurements can be performed before, during or after the flight is carried out. To
improve the quality, it is recommended that the field survey is performed after the post-
36
processing. In this way, open issues, which are detected during the post-processing, can be
checked in the field. This will ultimately result in higher data quality.5
Existing benchmark points can also be used for the validation, on condition that they are located
on a solid surface and can be transformed easily to WGS-84/EGM-96.
18.
INTERFEROMETRIC SYNTHETIC APERTURE RADAR
Figure: Workflow of IfSAR
The following preconditions have to be fulfilled:
- Benchmarks have to be marked (corner points) and their co-ordinates determined using
terrestrial survey;
- Flight plan based on:
o System characteristics (pulse rate, range, etc);
o Spatial accuracy requirements;
o Flight restrictions;
o Resolution requirements.
5
Existing benchmark points can also be used for the validation, on condition that they are located on a solid
surface and can be transformed easily to WGS-84/EGM-96.
37
19.
DATA COLLECTION TECHNIQUES FOR TERRAIN
The utilisation of specific techniques for the collection and processing of terrain
data will be outlined in this section.
20.
TERRESTRIAL SURVEY
Compared to obstacle mapping, conventional terrestrial surveying is much more efficient for
terrain data acquisition. Although the number of acquired points per work day is still much lower
than any aerial mapping technique, terrestrial survey has the advantage that the uneven
distribution of points, with the focus on Released Issue
Page 140 Edition: 2.0
Terrain and Obstacle Data Manual
breaklines and spot elevations, significantly reduces the amount of data collected. The terrain
model can then be derived from the surveyed points and breaklines, by building up a TIN.
In various studies, the possibility of mounting a GPS antenna on a car (operated in RTK mode)
to increase the survey efficiency has been examined. Even though the results are promising, with
respect to the achieved accuracy, this method does not meet the needs of aviation data because
the highest points are only randomly accessible by car.
In forested and urban areas with tall buildings, terrain data cannot be collected very efficiently
with GPS due to limited satellite visibility and signal strength.
21.
AIRBORNE LASER SCANNING
During data acquisition with ALS, ground and non-ground objects are not distinguished between.
Filtering, i.e. the removal of terrain points, is an important processing step in obstacle data
extraction. Therefore, the terrain data for Areas 1, 2, 3 and 4 can be derived from ALS-based
data acquisition, for very little additional cost. In the point cloud remaining after the filtering of
terrain points, trees / vegetation can be detected by using the multi-return capability of ALS. The
remaining points describe man-made objects which can, therefore, for a large part, be
automatically extracted (see also section 2.1).
22.
AERIAL PHOTOGRAMMETRY
As described for ALS, the imagery collected with aerial photogrammetry for obstacle mapping
allows the extraction of a DTM. If a DSM is generated using image correlation techniques, the
terrain extraction process is the same as for ALS. However, the reduced penetration in vegetated
areas results in fewer points on the ground which makes it difficult to achieve a “clean” DTM. If
vegetation and forests need to be extracted, less information is available for automated detection
in a DSM based on aerial photogrammetry than in a DSM based on ALS6.
Auxiliary information for vegetation detection can be provided with today’s digital cameras, where infrared
information is included in the imagery as a separate channel.
6
38
23.
INTERFEROMETRIC SYNTHETIC APERTURE RADAR
IfSAR provides the highest data acquisition rates from all currently available survey techniques.
The offered products also fulfil the quality requirements for Areas 1, 2 and 3.
The main drawbacks of the technique are the complex methods used in the signal processing
which reduces the number of companies able to provide IfSAR mapping services. On the
technical side, the inability to achieve good interferometric phase measurements for all locations
is still a major problem. The deviation of the field of view from nadir (sideward looking sensor)
causes portions of the terrain to not be captured because they are obscured by other parts of the
terrain or other objects. This shadow effect is typically exhibited in mountainous areas, whereas
in regions with flat terrain it only occurs in urban areas.
Depending on the wavelength, the signal is reflected from the topmost target (shorter
wavelength, X- or C-band) or tends to penetrate the vegetation canopy or ground (long
wavelength, L- or P-band). With soft ground, such as sand deserts, glaciers or snow, radar
signals are absorbed rather than reflected, also leading to data voids.
24.
COMPARISON AND RECOMMENDATION
In Figure 24, all four surveying techniques presented are compared using different criteria. This
comparison will provide recommendations as to which methods are most suitable, under which
circumstances, for an organisation. The most important factors to consider are:
ALS:
- Has very high capital costs and is, therefore, less widely available;
o A DTM can be extracted almost entirely automatically. Algorithms have been
commercially available for many years (allowing separation between data
acquisition and feature extraction);
o Terrain data acquisition is performed almost at no extra cost when combined with
obstacle mapping.
- IfSAR:
o There are only a few providers available due to the highest capital costs and
proprietary processing software of all the techniques;
o The efficiency of data acquisition is high, but is influenced by the need for
marked and surveyed corner points;
o For raw measurements, the penetration level is unclear which impacts the quality
in forested areas.
- Photogrammetry:
o Is the most efficient technique for data acquisition;
o The degree of automation is smaller, when compared to ALS, but the algorithms
are still evolving;
o The imagery can be used as a base for many other applications.
- Terrestrial survey:
o Has the lowest capital costs but is very labour intensive;
o Results in a well-structured terrain model (points, breaklines), with a minimum of
objects;
o Is ideal for data validation.
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Figure 24: Comparison of Different Sensor Techniques for Terrain Mapping
In the following table, recommendations on the survey methods for terrain are provided. The
symbols should be interpreted as follows:
‘++’ very suitable technically and very cost efficient;
‘+’ very suitable technically but not the most cost efficient;
‘o‘ suitable technically but very poor cost/benefit ratio;
‘- ‘ not meeting technical requirements and very poor cost/benefit ratio.
Table 2: Recommendation on Survey Methods for Terrain
ALS and aerial photogrammetry are only very cost efficient when Areas 3 and 4 are surveyed in
one survey campaign.
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DATA COLLECTION TECHNIQUES FOR OBSTACLES
25.
TERRESTRIAL SURVEY
Using conventional terrestrial survey for data acquisition is often inefficient because of the
limited visibility from one stand point (either due to obstructions in urban areas or due to limited
measurement range in the open field). For example, there is a risk of not obtaining reflection
from the targeted (thin) obstacle, but from the one behind it. It is difficult to detect such
erroneous measurements during data acquisition as no additional data is used for real-time
validation.
GPS/RTK measurements are not suitable for obstacle data acquisition due to the need to access
each obstacle to be surveyed.
26.
ALS
Several points should be considered when using ALS for obstacle mapping:
- To increase the probability that a thin object, like an antenna is captured, it is
recommended that the sensor is tilted and the radiometric resolution of the sensor is
calibrated.
- Environmental conditions: The humidity can have a strong impact on the strength of the
returned signal (local loss of signal). Strong winds or turbulence increase the possibility
that the gathered points are distributed unevenly. Therefore, meteorological restrictions
must be carefully observed during data collection.
- Obstacle detection: After pre-processing the different data streams (GPS, IMU, laser
scanner) and combining them, a digital point cloud is available for further process steps.
To detect obstacles, the points are separated into ground and non-ground points. The nonground points can then be compared with an ODCS and the points describing obstacles
can be easily detected. With a tilted sensor, it is expected that, for each object, there are
multiple pulses with almost identical x/y but different z co-ordinates registered.
Algorithms can help to determine the reliability of these identified objects. Where only a
single echo is registered, certain plausibility tests can help to determine if such an object
may or may not be an obstacle (for example, the reflection from a bird). In certain cases,
control survey with conventional terrestrial survey, is recommended.
- Feature extraction: Once points describing an obstacle are selected, they must be
combined and converted to some form of GIS object, i.e. point, line and polygon. The
degree of automation of such a process strongly depends on the quality requirements (i.e.
target applications) of the geometry. For further information, see Airborne Laser
Scanning for Airport Terrain and Obstacle Mapping (A Limited Feasibility Study)
[Reference 24].
- All processing steps can theoretically be performed by an organisation, independent of
the data acquisition provider. For practical reasons, it is recommended that data
acquisition and pre-processing are combined into one work package so that the first
deliverable is the geo-referenced point cloud. Feature extraction does not require ALS
capabilities and so, again, it can be performed by a different organisation.
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27.
AERIAL PHOTOGRAMMETRY
Several points should be considered when using aerial photogrammetry for obstacle mapping:
- A DSM can be generated using an image correlation process. This allows similar postprocessing steps to those described for ALS in section 7.2.3.3.
But the image correlation is, in some circumstances (low texture), not reliable and the DSM is
2.5D, not true 3D, as with ALS.
The manual interpretation of what has to be considered as an obstacle is labour intensive for
photogrammetric data, but, at present, much more reliable than image correlation. As the
operator has to define which objects are to be considered obstacles, human interpretation may
impact the data homogeneity and data quality.
Systems are available which support the operator by automatically generating the ODCS, based
on the ODCS specifications and the actual runway data. The ODCS is shown in the system so
that the differentiation of objects penetrating the ODCS, from other objects, is facilitated. In
contrast to the feature extraction in ALS, the human interaction in photogrammetric data
processing allows the combination of both the obstacle detection and feature extraction steps,
resulting in high-quality, true 3D vectors.
28.
IFSAR
Obstacle detection from IfSAR data suffers from low reliability since the reconnaissance largely
depends on the incident angle. Power lines, for example, are clearly visible in SAR imagery, if
running parallel to the flight direction, but are not detectable if running across the flight
direction. The reason for this problem is the “layover” effect, whereby points appear to be
reversed in the imagery, e.g. where point A is in front of point B, the imagery reverses them so
that point B appears to be in front. Layover causes a loss of useful signal and, therefore,
precludes the determination of elevation in layover regions.
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29.
COMPARISON AND RECOMMENDATIONS
In Figure 25, the surveying techniques appropriate for obstacle mapping are compared using
different criteria. This comparison will provide recommendations as to which methods are most
suitable, under which circumstances, for an organisation. The most important factors to consider
are:
- ALS:
o Has the highest capital costs and, therefore, is less widely available;
o It already offers the highest degree of automation but further development is
expected;
o Has the lowest risk of missing an obstacle during data acquisition.
- Photogrammetry:
o Is the most efficient technique for data acquisition;
o The degree of automation is smaller, when compared to ALS, but the algorithms
are still evolving;
o The risk of missing an obstacle is higher, when compared to ALS, but due to
manual interaction, the quality of the resulting obstacle is expected to be higher
than all other techniques.
- Terrestrial survey:
o Has the lowest capital costs but is very labour intensive;
o Is a mature technique but not much further improvement is expected;
o The risk that an obstacle is missed is higher than with the other techniques and,
therefore, the level of effort needed for validation is high;
o Is ideal for data validation.
- IfSAR:
o Obstacle detection suffers from low reliability. At the time of writing this Manual,
the technique not suitable for obstacle data collection.
Figure 25: Comparison of Different Surveying Techniques for Obstacle Mapping
43
In the following table, recommendations on the survey methods for obstacles are provided. The
symbols should be interpreted as follows:
‘++’ very suitable technically and very cost efficient;
‘+’ very suitable technically well suited but not the most cost efficient;
‘o‘ suitable technically but very poor cost/benefit ratio;
‘- ‘ not meeting technical requirements and very poor cost/benefit ratio.
Table 3: Recommendation on Survey Methods for Obstacles
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30.
SIZE OF DATA
It is clear that what was considered to be a large data set a decade ago is significantly different to
that which is considered to be a large data set today. In fact, today, systems capable of handling
terabytes of data are not uncommon.
An example of the sizes of terrain and obstacle data was provided on EUROCONTROL’s
Terrain and Obstacle Data Forum. For an area of 49,000 km2, the size of a file with the elevation
grid is 62.8 Megabytes (MB). The size of the same data, stored as a binary database, in which
every point has its geographical co-ordinates and elevation, is 657 MB.
Whilst the potential size of the data to be processed in relation to terrain and obstacle data is
significantly larger than the traditional AIP data handled by AIS, managing data of this size is
neither new nor unique to AIS.
For example, in the aviation sector, many AIS or airport authorities use GIS for handling spatial
data. Often high-resolution imagery (orthophoto), with ground sampling distance of 25–50cm, is
stored within the GIS database and used in a variety of GIS applications. The size of data in such
data sets is relatively high when compared with the size of the AIP in digital form.
In the banking sector, data related to each and every transaction is stored and thousands of
transactions are processed every hour of the day. Closely linked to aviation is meteorology,
where large volumes of data are processed to produce displays indicating temperature, wind
speed, pressure and humidity, as well as time and three spatial dimensions. In total, this equates
to terabytes of data.
Hydrographic offices provide another example, as they process large volumes of maritime data.
In some cases, they cover large areas of the world, rather than just the territory of a single State.
45
With regards to the formats to be used for terrain and obstacle data, databases, American
Standard Code for Information Interchange (ASCII), binary Digital Terrain Elevation Data
(DTED), GEOTIFF and comma-separated values (CSV) have all been considered and it is
recommended that consideration is given to the data that is available and how this may be used
within the applications that are likely to be used by the end-users. The development of new
standards for the ISO 19100 series is also ongoing and it is further recommended that the work
of the OGC, which acts as the technical committee for these standards, is monitored.
31.
NEW METADATA ABOUT A FEATURE (OR FEATURE TIMESLICE)
An important aspect of aeronautical information is its temporal validity. Almost every piece of
aeronautical information has an effectivity date attached to it. While ISO 19115 [Reference 16]
provides some means of modelling temporal extents, aeronautical information can benefit from
an extended model, with strong emphasis on temporal validity. AIXM presents a model that
allows for explicit modelling of temporal validity.
The AIXM temporality model defines the entity “AIXMTimeSlice” which allows all changes
during a feature’s lifetime to be associated with the corresponding feature. The grouping of a
feature’s changes allows for a complete history of the evolution of a single feature. When
applying the concept of “time slices” to an AIS/AIM system, it is possible to submit queries to
the AIS/AIM system, such as “show me the information about this feature as of 2008/01/02”.
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32.
DOGAMI LIDAR VIEWER
http://www.oregongeology.org/dogamilidarviewer/
This interactive map allows you to view 9 ft resolution lidar data for portions of the state of
Oregon. Lidar (light detection and ranging) is a tool that provides very precise, accurate, and
high-resolution images of the surface of the earth, man-made infrastructure, and vegetation.
The Oregon Department of Geology and Mineral Industries (DOGAMI) has been involved in
efforts to collect high-resolution lidar in Oregon since 2003. In 2007, DOGAMI formed the
Oregon Lidar Consortium (OLC) to develop cooperative agreements for the collection of highquality lidar that benefits the public at large, the business community, and agencies at all levels
of government. Since then DOGAMI has collected over 13 million acres of lidar throughout
Oregon and the Northwest.
Built on ArcGIS Server 10 and the ArcGIS API for Flex version 2.3.1, the Lidar Data Viewer
enables DOGAMI to serve up terabytes of lidar data using Esri's optimized cached map services.
DEM grids and hillshades were derived by county and are stored in file geodatabases. A web
service is published and cached for each county where lidar exists.
3ft resolution lidar is available for purchase by lidar data quad. Use the search tool in the
flexviewer to search for and purchase lidar quads.
Flexviewer Application Development: Paul Ferro Lidar Processing: John English, Paul Ferro
DOGAMI's Web Services Directory is not available for public use at this time
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LIDAR TOLL from ESRI LAS DATA SET TOOLS
http://www.arcgis.com/home/item.html?id=d8782286e3c9442bb5c244bf39da5966
http://www.oregongeology.org/slido/index.html
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"LIDAR" SURVEYS
33.
LIGHT DETECTION AND RANGING
We utilise the latest technology in the form of Lidar surveying methods were we offer the
following unique capabilities that will assist our clients to maximize the benefits offered by
LiDar scanning. Our clients can have the confidence that we will provide innovative technology
with high accuracy and fast data capture, a proven survey process that ensures accuracy,
completeness and consistency. In addition we provide unmatched experience for fast, safe and
complete results, utilising the latest software to achieve maximum return on investment
pertaining to our professional service.
34.
HOW DOES IT WORK?
Lidar Simultaneously:
- Measure trajectory of aircraft in three dimensions
- Measure orientation of laser scanner about three rotations axes
- Transmit and receive laser pulses, measure the time-of-flight (i.e. range to reflecting
surface)
Consequently LIDAR
- Know the coordinates of thousands of points surveyed per second
- Map the surface of the Earth in high density
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35.
CLICK HERE TO SEE A VIDEO OF THIS SERVICE
36.
DELIVERABLES
Point Cloud
Comprised of millions of points collected from the Laser onboard the aircraft, the Point Cloud is
combined with IMU and GPS data to ensure that every point in the cloud is within sub 10cm
accuracy
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Imagery
Hi resolution ortho-rectified photos are overlaid on the data to create extremely high detailed
maps. Using a 39 Mega Pixel Medium format camera to ensure the highest resolution and
quality.
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Contours
A contour line joins points of equal elevation above a given level, such as mean sea level. A
contour map is a map illustrated with contour lines, for example a topographic map, which thus
shows valleys and hills, and the steepness of slopes. The contour interval of a contour map is the
difference in elevation between successive contour lines.
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DTM
Digital Terrain Model (DTM) is created by digitally removing all of the cultural features inherent
to a DTM by exposing the underlying terrain. The quality of a DTM is a measure of how
accurate elevation is at each pixel (absolute accuracy) and how accurately is the morphology
presented (relative accuracy). Several factors play an important role for quality of DTM-derived
products:
- Terrain roughness
- Sampling density (elevation data collection method)
- Grid resolution or pixel size
- Interpolation algorithm
- Vertical resolution
- Terrain analysis algorithm
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37.
USES FOR LIDAR SCANNING
3D City Models
DTM of Large areas
Calculation of accurate Volumes over large areas, being much more cost effective than
conventional surveys
- Updating of Statutory Mining plans
- Roads / Rail and Power line routes for Planning and Design
- Measuring of Carbon Credit
- Bulk property valuations
Please contact us should you want any more detail of the above
http://www.africansurveyors.com/lidar.html
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38.
TECHNICAL BACKGROUND OF LIDAR
Technical Introduction
Light Detection and Ranging (LiDAR) is a surveying technique which enables highly accurate,
rapid and high-density three-dimensional mapping of large areas.
The Street and Air Mapper LiDAR system as used by ACS is superior to any other LiDAR
system on the African continent, due to its very high scan rate and the low flying altitude, which
yield point densities of up to five times that of older generation LiDAR systems. Our Riegl
VQ450 scanner has and effective 360 Degree measurement rate of up to 550,000 points per
second. A point cloud density of up to +-100 point per Square meter can be expected by flying at
very low altitudes (+-30m AGL).
In addition, high resolution camera flown in conjunction with the LiDAR system yields fullcolour, geo-referenced orthophotos at the highest possible resolution of up to +-1cm per pixel by
flying at very low altitudes (+-30m AGL).
Surveying an area of interest using LiDAR and high-resolution photography would save the
client time, money and in some cases the logistic requirement of providing surveyors with access
to the area.
Mission Planning and Preparation
Appropriate mission planning will ensure the highest possible accuracies of surveyed data. The
following factors are taken into account when deciding on the best time to conduct the survey:
- The GPS satellite constellation, which has a 23 hours and 56 minutes repeat cycle, needs
to be taken into account to maximise the number of satellites available when conducting
the survey. The Position Dilution of Precision (PDOP) is a quantification of how
accurately one would be able to measure positions at a given time. ACS will conduct the
survey during a time window, determined for the area of interest, during which PDOP is
sufficiently low (typically below 3.5).
For safety purposes and to ensure data quality, the weather conditions are taken into
account. LiDAR surveys are not recommended in high winds (over 30 knots) or when
visibility is poor. Because of the lower flying altitude employed ACS (typically below
500 m), surveys can even be conducted during cloudy periods; however, very dense lowlevel fog will force surveying to be postponed until the weather improves.
56
A GPS base station has to be set up during the aerial survey within 25 km of the survey
area. ACS uses 2 state-of-the-art Trimble R8 GPS receivers as base stations, which are
operated on the ground during the aerial survey. Collected data can then be used during
post-processing to find accurate differential positions of the helicopter along its
trajectory.
- The sun angle is taken into account when selecting an appropriate survey time window.
In order to obtain good orthophotos, surveys are typically conducted between 09:00 and
15:00 local time.
The accuracy obtained for measurements of the LiDAR system’s position along the aircraft
trajectory should be within 2.5 cm horizontally and 3.5 cm vertically. The obtained accuracies
will be reported with the results.
-
Data Processing Workflow
The process of deriving mapping products from LiDAR survey data can be summarised as
follows:
- Trajectories are determined for the LiDAR system along the helicopter’s flight path. Firstly,
differential GPS data (relative to the GPS base stations) are processed using the NovAtel
Waypoint software. Thereafter, the GPS-derived trajectory is refined by incorporating
inertial measurement unit (IMU) data in Leica’s IPAS Pro software.
- The Streetmapper software is used to combine the measured laser ranges with the positions
(from differential GPS) and attitude (from IMU measurements) to produce a so-called laser
point-cloud. This point-cloud contains all the spatial information from the survey.
- All surveyed data will be in UTM or WGS84, and projected the projection specified
beforehand by the client.
- TerraScan is used to classify all the point-cloud data, based on observed intensities and threedimensional coordinates, to different classes, including ground, vegetation, buildings. etc.
- Contouring and DTM/DEM generation is achieved through the use of established processing
techniques in the TerraModeler software.
- Orthophotos are merged and rectified using the TerraPhoto software.
- Quality checks are conducted by comparing the aerial survey data with ground control.
Orthometric heights will, unless otherwise specified in this document, be determined by
applying the EGM96 geoid model to the survey data and fitting it to local trigonometric
beacons, if available and required.
The above-mentioned process will ensure the timely delivery of the client’s requested products
to the highest possible degree of accuracy.
Personnel & Equipment
The following staffs are typically made available on most of our projects:
- 1 Project Manager
- 2 Pilots
- 1 System Operator
- 6 Data Processors
- 1 Base Station Operators
- 1 Surveyor for Ground Control
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Helicopter
Most of our International LiDAR projects are flown with a cost effective Robinson R44. The
R44 is a single-engined helicopter with a semi-rigid two-bladed main rotor and a two-bladed tail
rotor and a skid landing gear. It has an enclosed cabin with two rows of side-by-side seating for a
pilot and three passengers. Tail rotor direction of rotation on the R44 is reversed. On the R44 the
advancing blade is on the bottom.
Designed during the 1980s by Frank Robinson and his staff of engineers, the R44 first flew on
March 31, 1990. The R44 Astro was awarded an FAA Type Certificate in December 1992, with
the first deliveries taking place in January 1993. In January 2000, Robinson introduced the
Raven with hydraulically-assisted controls and adjustable pedals. In July 2002, Robinson
introduced the Raven II featuring a more powerful, fuel-injected engine and wider blades,
allowing a higher gross weight and improved altitude performance
Accuracy
LiDAR accuracies are reported at a 68% confidence level ("one sigma") with ellipsoidal heights.
We use the root-mean-square error (RMSE) to estimate positional accuracy. RMSE is the square
root of the average of the set of squared differences between dataset coordinate values and
coordinate values from an independent source of higher accuracy for identical points. Accuracy
is reported in ground distances at the 68% confidence level. Accuracy reported at the 68%
confidence level means that 68% of the positions in the dataset will have an error with respect to
true ground position that is equal to or smaller than the above reported accuracy value, thus when
100 points are tested, the 68% confidence level allows 32 points to fail the thresholds of the
above stated accuracies
Horizontal absolute accuracies
To guarantee horizontal absolute accuracies it is required to place and survey ground control
beacons throughout the site. As a rule of thumb, we need a minimum of 5 ground control points
and 1 additional ground control point for every 2,000Ha above 10,000Ha evenly spread-out
throughout the site. When using ground control the horizontal absolute accuracy will remain the
same as the relative horizontal accuracy mentioned in the financial proposal.
Vertical absolute accuracies
All LiDAR system uses ellipsoidal GPS measurements, thus only ellipsoidal heights will be
delivered however for South African projects we will be applying the latest available South
African Geoidal Model, which is accurate up to 10cm. Thus, using GPS Technology together
with our LiDAR system an absolute Orthometric vertical accuracy of +-10cm can be expected.
For countries that do not have its own Geoidal model an absolute vertical accuracy cannot be
guaranteed. Orthometric accuracy are subject the accuracy of the latest World Geodetic Model
(Currently EGM 2008).Previous experience with EGM 2008 proved to be accurate within +20cm, but may differ from country to country and if the project does not exceed a 30km radius.
The absolute Vertical accuracy can be increased to match the relative vertical accuracies as per
our financial proposal by levelling the ground control beacons. This service is usually not
included in our financial proposals unless it is included in our financial proposal. This will be a
very costly and timeous exercise. However, it is a service that can be performed at a later stage if
required.
58
Please note: If the client prefer not to have the beacons levelled then it is important that during
construction the contractors will need to be made aware of this, and ensure that, they work with
the ellipsoidal heights and not Orthometric heights. This is however only a concern for project
exceeding a 30km radius.
Our Equipment
ACS uses two of the latest LiDar systems to be produced by the German Riegl and IGI
manufacturers, which is also the newest LiDar equipment in South Africa.
LMS-Q560
The RIEGL LMS-Q560 is a revolutionary 2D laser scanner applying the latest state-of-the-art
digital signal processing technique which meets the most challenging requirements in airborne
laser scanning.
The RIEGL LMS-Q560 gives access to detailed target parameters by digitizing the echo signal
online during data acquisition, and subsequent off-line waveform analysis. This method is
especially valuable when dealing with difficult tasks, such as canopy height investigation or
target classification.
The operational parameters of the RIEGL LMS-Q560 can be configured to cover a wide field of
applications. Comprehensive interface features support smooth integration of the instrument into
complete airborne scanning systems. The instrument makes use of the time-of-flight distance
measurement principle of nanosecond infrared pulses. Fast opto-mechanical beam scanning
provides absolutely linear, unidirectional and parallel scan lines. The instrument is extremely
rugged, therefore ideally suited for the installation on aircraft. Also, it is compact and lightweight
enough to be installed in small twin- or single-engine planes, helicopters or UAVs. The
instrument needs only one power supply and GPS timing signals to provide online monitoring
data while logging the precisely time-stamped and digitized echo signal data to the rugged
accompanying digital data recorders RIEGL DR560 or DR560-RD. These high performance data
storage devices are capable of handling the continuous high speed data stream. The Data
Recorder DR560-RD, using two removable disks for smooth operation, supports RAID 1 to
achieve higher data integrity and RAID 0 for increased data throughput. Additionally an online
data integrity check is performed prior to transferring the full waveform data to the hard disks.
RIEGL VQ-450
The RIEGL VQ-450 is a very high speed, non-contact profile measuring system using a narrow
infrared laser beam and a fast line scanning mechanism, enabling full 360 degree beam
deflection without any gaps. It is characterised by a Laser Pulse Repetition Rate (PRR) of up to
550 kHz and a scanning rate of up to 200 lines per second. Multitarget capability based on echo
digitization and online waveform analysis offers superior measurement capabilities even under
adverse atmospheric conditions
Inertial Measurement Unit (IMU)
The CCNS4 (Computer Controlled Navigation System, 4th generation) is a guidance, positioning
and management system for aerial survey flight missions.
The basic system consists of the Central Computer Unit (CCU), the 5'' TFT Command and
Display Unit (CDU), a state-of-the-art GPS receiver with antenna, necessary cabling and a
shock-absorbing mounting plate. The system is universally usable and can operate and integrate
all common digital and analog aerial camera systems. Together with IGIplan, it provides a
complete and comprehensive solution for mission planning, aircraft guidance and sensor
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management. The CCNS4 controls the camera and other sensors, including crab/drift setting(s),
forward overlap, V/H computation and provides data for data annotation on film; the coordinates
may be WGS 84 or the country's X/Y - coordinates. The CCNS4 has the benefit of a fully
automated flight control system for aerial surveying and reconnaissance. A pilot's Control &
Display Unit (primary) and an operator's Control & Display Unit (secondary) - both 5 inch TFT are available. All operations are activated easily via one control dial and five buttons. The EFIS
type display, which is operated like an aircraft instrument, is divided into guidance and
system/sensor management information (right side of the TFT). The pilot merely has to "follow
the line". CCNS4 features outputs with selectable sensitivity for HSI and CDI instruments.
The CCNS4 requires position and velocity information from a GPS receiver and optional
directional information from the aircraft's directional gyro (DG). The CCNS4 can be operated by
a variety of external GPS receivers that already may be installed in the aircraft by using the
receiver specific data format or the NMEA 0183 data format. The integrated GPS receiver
(DGPS) operates according to the RTCM-104 format and can receive real-time differential
corrections from WAAS and EGNOS satellites. Directional gyro information is used by a
Kalman filter process for stable position information and drift/crab calculation. Corrections for
local variations and aircraft deviations can be used. AEROcontrol is IGI's GPS/IMU system for
the precise determination of position and attitude of an airborne sensor. All operations and the
management of the AEROcontrol system is controlled by the CCNS4. All raw data of the IMU
are stored on the AEROcontrol system. The software uses a forward/backward Kalman filter
algorithm to achieve optimal results. The CCNS4 is able to control up to two sensor systems.
The actual flight data - including the aircraft's position in WGS 84 coordinate or local grid
system - are computed and can be provided for data annotation on film. Waypoint/photo data,
flight information and GPS positions are stored and transferred to the CCNS4 Mission Card for
post processing, analysis and plotting of the flight index or the complete mission. The system has
the advantage of no mechanical (moving) parts, no hard or floppy disk to crash or wear out from
dust, humidity, acceleration or vibration. More than 300 installations - worldwide - show that the
CCNS4 is a very reliable system. Using the CCNS4, no specialized photo pilot or photo
navigator is required.
GPS Base Stations
The Trimble R8 GPS System is a multi-channel, multi-frequency GPS receiver, antenna, and
data-link radio combined in one compact unit, with the following features
- Advanced Trimble Maxwell™ Custom Survey GNSS Chip;
- High precision multiple correlator for GNSS pseudorange measurements;
- Unfiltered, unsmoothed pseudorange measurements data for low noise, low multipath
error, low time domain correlation and high dynamic response;
- Very low noise GNSS carrier phase measurements with <1 mm precision in a 1 Hz
bandwidth;
- Signal-to-Noise ratios reported in dB-Hz;
- Proven Trimble low-elevation tracking technology; and
- 72 Channels: GPS L1 C/A Code, L1/L2 Full Cycle Carrier.
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Quality
The following steps are taken to ensure that the client’s products meet the set requirements:
- All internal offsets within the LiDAR system are to be calibrated twice a year, as per the
Street/Air Mapper system specifications. ACS’s last system calibration was done in
October 2011 during which vertical accuracies, compared to surveyed ground control
points, of < 2.5 cm were obtained. Furthermore, the system’s lever-arm measurement
(offset between the GPS antenna and the system’s internal reference point) was surveyed
to sub-centimetre level and certified by an independent registered professional surveyor
in October 2011.
- To ensure the highest possible relative accuracies, a flight line perpendicular to the lines
covering the area of interest, is to be flown at the end of the survey. Overlapping data
should correspond to each other at levels within the product specification.
- A further quality check is incorporated in the data processing algorithm, by manually
inspecting data in the TerraScan software, to check for any un-calibrated offsets between
data from different flight lines.
- The obtained point cloud could be compared to a sufficient number of ground control
points (GCPs) which are surveyed onsite before or after the actual LiDAR survey,
thereby ensuring the accuracy and quality of the data.
Although all steps possible will be taken to ensure data accuracies, ACS will not be liable for any
inaccuracies due to inaccuracies in the trigonometric network used.
LiDAR Penetration
We cannot guarantee evenly spread LiDAR penetration to the ground in tropical rainforests.
However, based on previous experience in Liberia we managed to generate accurate 0.5m
contours with +-5 points per square meter with tree canopies reaching heights of up to 70m.
Lasers do not reflect from water, thus no LiDAR points can be expected over water surfaces.
Vegetation penetration percentages can be expected to be as follow:
 Light Bush – 50%
 Grasslands – 40%
 Fynbos – 20%
 Dense Bush – 15%
 Rain Forest – 5%
 Water – 0%
Aircraft safety
All legislation regarding aviation will be strictly adhered to during the survey, to ensure the
safety of the survey team, as well as lives and property around the survey site.
Eye safety
Our Street and Air Mapper system is eye safe as an FDA certified Class 1 laser
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Safety Plan
A comprehensive safety file can be made available once the proposal has been accepted and all
the project details have been transferred to us.
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BIBLIOGRAPHY IN CONSTRUCTION:
ICAO ANNEXE 15
ESRI WHITE PAPER
EUROCONTROLE
MANY OTHERS (ALL LINK IN THE DOCUMENTS)
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