UNSD Workshop
Mobile GIS
Pieter van Jaarsveld
Mobile GIS Specialist
An Overview to a professional GPS/Mapping collection solution
UNSD - Mapping and Sensus Workshop: Lusaka, Zambia 8 -12
October 2007
Slide 1
Mobile GIS
Survey
Recreational GPS users?
In-car navigation users?
Capturing GPS data in the field for GIS use?
Plan to in the next year?
UNSD - Mapping and Sensus Workshop: Lusaka, Zambia 8 -12
October 2007
Slide 2
Global Positioning System
Mobile GIS
UNSD - Mapping and Sensus Workshop: Lusaka, Zambia 8 -12
October 2007
Slide 3
Mobile GIS
What is GPS?
Global Positioning System
• Where on earth am I ?
Constellation of satellites
Handheld devices
Various Applications
Accuracy
UNSD - Mapping and Sensus Workshop: Lusaka, Zambia 8 -12
October 2007
Slide 4
GPS in 5 Basic Steps
Mobile GIS
3
2
Use ephemeris
for satellites’
location
Accurate clocks
are required
1
4
Correct for
Atmosphere &
Ionosphere
5
Differential
Corrections
Trilateration using
speed of light
UNSD - Mapping and Sensus Workshop: Lusaka, Zambia 8 -12
October 2007
Slide 5
Mobile GIS
UNSD - Mapping and Sensus Workshop: Lusaka, Zambia 8 -12
October 2007
Slide 6
Mobile GIS
Control Segment
Provides worldwide coverage and control
• 365/24/7
Master Control station
• Colorado
Four support stations
•
•
•
•
Hawaii
Kwajalein
Diego Garcia
Ascension Island
UNSD - Mapping and Sensus Workshop: Lusaka, Zambia 8 -12
October 2007
Slide 7
Mobile GIS
Space Segment
GPS satellite constellation
• 24 satellites
• Replenishment occurring
Satellite design
12
10
Number
• Lifetime 7.3 years
• 16 satellites over
9 years old
28 Satellites in GPS Constellation
8
6
4
2
0
Under 3
3-4
5-6
7-8
9-10
Age (Years)
UNSD - Mapping and Sensus Workshop: Lusaka, Zambia 8 -12
October 2007
Slide 8
11-12
13+
Mobile GIS
User Segment
Equipment produced by Military and Private
companies
Receives signal and computes
• Position
• Time
• Velocity
UNSD - Mapping and Sensus Workshop: Lusaka, Zambia 8 -12
October 2007
Slide 9
How do we position ourselves?
Mobile GIS
Simple Geometry
• Velocity times vs travel time
Determine Radio Wave Time Travel
• Accurate timing
Measure Distances
• Known orbit locations
Trilateration
• Distances not angles
UNSD - Mapping and Sensus Workshop: Lusaka, Zambia 8 -12
October 2007
Slide 10
Sources of Positioning Error
Mobile GIS
Ionosphere and Atmospheric delays
Satelite and receiver Clock Error
Multipathing
Dilution of Precision
Receiver Issues
Selective Availability
UNSD - Mapping and Sensus Workshop: Lusaka, Zambia 8 -12
October 2007
Slide 11
Mobile GIS
•
•
Two receivers track the SAME signals and errors
at the SAME time
Derived corrections are then applied to the data
during postprocessing
–
•
Differential GPS
GPS Analyst contains tools for DC
Does not correct multipath
Data
Collector
Base
UNSD - Mapping and Sensus Workshop: Lusaka, Zambia 8 -12
October 2007
Slide 12
Mobile GIS
Differential Correction
Red = Uncorrected
GPS
Green = GPS after
differential correction
UNSD - Mapping and Sensus Workshop: Lusaka, Zambia 8 -12
October 2007
Slide 13
Mobile GIS
Selecting a GPS
Recreational versus Professional GPS
Accuracy
• Tens of meters versus sub meter
GIS data integration
• Format conversion
Attribute collection
• Customised forms, business rules
UNSD - Mapping and Sensus Workshop: Lusaka, Zambia 8 -12
October 2007
Slide 14
Mobile GIS
Data Collection Software
UNSD - Mapping and Sensus Workshop: Lusaka, Zambia 8 -12
October 2007
Slide 15
Data Collection Workflow
Mobile GIS
Server
(server to server)
Desktop
Mobile
Export to PGDB
Enterprise
Geodatabase
Check out
Copy to device
Server
Desktop
Copy to Desktop
ArcPad
Check In
Data
validation
Post process
UNSD - Mapping and Sensus Workshop: Lusaka, Zambia 8 -12
October 2007
Import to
Enterprise
Slide 16
Mobile GIS
Data - things to remember
Check out and post processing is performed on a
personal geodatabase NOT directly from
enterprise. WHY?
•GPS detail not required in enterprise
•Topology not supported in GPS Analyst
Carefully choose extents. WHY?
•Large extent limits the amount of data capture
Current only personal geodatabase support,
efforts to supporting file geodatabase underway.
UNSD - Mapping and Sensus Workshop: Lusaka, Zambia 8 -12
October 2007
Slide 17
UC 2007 Tech Sessions
17
Mobile GIS
What is ArcPad?
•Part of ESRI overall mobile strategy
•A mobile GIS application for field mapping
applications
•Designed for broad range of mobile systems
•Allows input from GPS receivers, rangefinders,
digital cameras and other devices
•Provides a generic set of mobile GIS functionality
•Extensive customization capabilities
•Extends Geodatabase to the field through
disconnected editing
UNSD - Mapping and Sensus Workshop: Lusaka, Zambia 8 -12
October 2007
Slide 18
What can you do with ArcPad?
Mobile GIS
•
•
•
•
•
•
•
•
Use your existing data
Add data from the Internet
Move around your map
Query your data
Edit your data
Measure distance, area, and bearings on your map
Navigate with your GPS
Customize ArcPad to streamline your workflow
UNSD - Mapping and Sensus Workshop: Lusaka, Zambia 8 -12
October 2007
Slide 19
Mobile GIS
ArcPad Benefits
Streamlines the workflow
• Smart, task oriented solutions
Increases productivity
• Reduces office work and data entry time
• Improves the accuracy of data
• Resulting in more accurate and current data for
analysis and decision making
UNSD - Mapping and Sensus Workshop: Lusaka, Zambia 8 -12
October 2007
Slide 20
Mobile GIS
ArcPad Functionalities
Improved performance
Enhanced editing tools
• Snapping
• Undo
• offsets for points, lines, polygons
• repeated features
• segmented line features
Camera and rangefinder support
Improved symbology and labeling
Support for Graphics layer
• for redlining or mark-up
Import/export tools for ArcGIS
Customization
• wizard for creating custom forms
UNSD - Mapping and Sensus Workshop: Lusaka, Zambia 8 -12
October 2007
Slide 21
Mobile GIS
ArcPad Functionalities
Significant performance gains on startup time
• Pre-buffering input
• Affects Applets, Layers, Scripts etc. (i.e ALL XML and
Scripts)
• Delayed loading of projection data
Usability enhancement
• Datum conversion wizard
• Picture browsing capabilities on Windows Mobile 5 devices
• Additional language packs available
Quality improvements
• About 80 bugs have been identified and fixed!
Minor feature improvements
• Object model improvements (Picture chooser, File object ,
Inter-process methods)
UNSD - Mapping and Sensus Workshop: Lusaka, Zambia 8 -12
October 2007
Slide 22
Mobile GIS
Configuring the GPS
Protocol = “Trimble GPSCorrect” or “NMEA0183”
Port = “COM3: TSIP Serial Port (GeoExplorer)
Port = “COM7: TSIP Serial Port (JunoST)
Port = “COM2: TSIP Serial Port (Recon XC)
UNSD - Mapping and Sensus Workshop: Lusaka, Zambia 8 -12
October 2007
Slide 23
Mobile GIS
Streaming and Averaging
Averaging
number of incoming GPS position
coordinates that ArcPad uses for
calculating an average coordinate
Streaming
Position Interval = How frequently
ArcPad uses incoming GPS
coordinates
Distance Interval = ArcPad uses
incoming GPS coordinates only
when greater than this distance
from LAST coordinate used
UNSD - Mapping and Sensus Workshop: Lusaka, Zambia 8 -12
October 2007
Slide 24
Mobile GIS
GPS Preferences
Quality
Minimum and maximum values can be
predefined
Can be made compulsory to ensure
data integrity
Warning and Alerts
Visual and Audio alerts
Constantly warns the user if not
complying to presets
Will inform the user of GPS status
Can be annoying
Can be switched off
UNSD - Mapping and Sensus Workshop: Lusaka, Zambia 8 -12
October 2007
Slide 25
Mobile GIS
Editing using the GPS
Firstly, make layer
editable (one point,
line, polygon, at a
time)
Then select feature
type
UNSD - Mapping and Sensus Workshop: Lusaka, Zambia 8 -12
October 2007
Then select GPS
capture tool
Slide 26
Mobile GIS
Ensuring data quality
Elevation Mask
Default 15
No. of Satellites
Min of 4 SV’s
SNR
Signal to
Noise Ratio
DOP
High = Accurate
Low = Productive
SV Geometry
High = BAD
Low = GOOD
UNSD - Mapping and Sensus Workshop: Lusaka, Zambia 8 -12
October 2007
Slide 27
UC 2007 Tech Sessions
27
Mobile GIS
ArcPad with other devices
ArcPad can be used with:
• Digital Cameras
• WiFi enabled cameras
• BT enabled camerasUse “Camera” tool
• Photo Layer
• Custom Form
• Laser Rangefinders
• What is your accuracy needs?
• External GPS
UNSD - Mapping and Sensus Workshop: Lusaka, Zambia 8 -12
October 2007
Slide 28
Mobile GIS
Data Collection Techniques
Where are the Satellites?
• Your Body is an obstruction!
Point Data Collection
• Position First and Attributes Second
Polyline & Polygon Collection
• Streaming (less accurate but dynamic)
• Vertex Averaging (more accurate and static)
UNSD - Mapping and Sensus Workshop: Lusaka, Zambia 8 -12
October 2007
Slide 29
UC 2007 Tech Sessions
29
Mobile GIS
ArcPad Tips and Tricks
•Do you understand Sticky Keys?
•Have you used appropriate colours and line
thicknesses?
•Is your device locked?
•Don’t you pick on me! (Avoid clicking on the map)
•The art of using a stylus
•Slow down and smell the flowers! 
UNSD - Mapping and Sensus Workshop: Lusaka, Zambia 8 -12
October 2007
Slide 30
UC 2007 Tech Sessions
30
Mobile GIS
ArcPad Orientation Demonstration
UNSD - Mapping and Sensus Workshop: Lusaka, Zambia 8 -12
October 2007
Slide 31
Mobile GIS
Thank you
Mobile GIS Specialist
pvanjaarsveld@gims.com
(011) 238 6300
UNSD - Mapping and Sensus Workshop: Lusaka, Zambia 8 -12
October 2007
Slide 32