TRIM DOC:
ISSUE DATE:
D10#9571
04/02/2010
WALIS Road Group
Landgate Road Centreline with IRIS Data Overlayed
Analysis Report
CONTENTS
Modelling Roads
Road and Route Analysis
Conclusion
This document is owned and authorised by the Manager Asset and Network Information
Branch. Please submit all comments and requests to the Senior Spatial Analyst, the
delegated custodian.
All controlled copies shall be marked accordingly
Document Control
Date
05/11/2009
31/12/2009
14/01/2010
03/02/2010
Version
0.1
0.2
0.3
1.0
Status
Draft
Draft
Draft
Final
Description
Initial draft
Peer review
Management review
Management Approval
Author
Daniel Grillo
Daniel Grillo
Daniel Grillo
Daniel Grillo
Authorised by Manager Asset and Network Information 03/02/2010
Revision Status Record
Section
Page
No.
Version
Description
Author
1.1
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Index
PREFACE .............................................................................................................................................................. 4
BACKGROUND ............................................................................................................................................................. 4
HOW TO USE THIS DOCUMENT ....................................................................................................................... 4
ABBREVIATIONS AND DEFINITIONS ............................................................................................................... 5
SECTION 1 – MODELLING ROADS ................................................................................................................... 6
TYPICAL GIS MODEL .................................................................................................................................................. 6
LINK-NODE MODEL ..................................................................................................................................................... 7
SECTION 2 – ROAD AND ROUTE ANALYSIS ................................................................................................. 9
ROAD NUMBER ........................................................................................................................................................... 9
ROUTE ANALYSIS ...................................................................................................................................................... 10
SECTION 3 – CONCLUSION ..............................................................................................................................15
CONCLUSION ............................................................................................................................................................. 15
OTHER ISSUES ............................................................................................................................................................... 16
Digitised Direction of Roads ................................................................................................................................. 16
Spatial Topology ................................................................................................................................................... 16
Roads not assigned a Designated Custodian ........................................................................................................ 16
Road Lengths ........................................................................................................................................................ 16
APPENDIX B: REFERENCE DOCUMENTS .....................................................................................................17
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Preface
For a number of years Landgate have been tagging road centreline managed and
maintained within their organization with the Main Roads Western Australia road
identification number.
At an October 29th 2009 WALIS Road Group (RRCN meeting), the question was posed
about the purpose and value of tagging. It was suggested that the value of tagging was to
identify management and ownership of each road section. At that meeting, Main Roads
representative to the group suggested that the tag could provide a means of adding Main
Roads stored road attributes to Landgate road centreline.
This report is prepared for members of the WALIS Road Group and is indented to:

Assess
the completeness of tagging on the Landgate Road Centreline;

Report
the ‘end benefit’ of tagging beyond identifying ‘management/ownership’; and

Make any
conclusions/recommendations to the group for further discussion.
The work completed in this report used ESRI ArcGIS software (9.3.1). Currency of
Landgate centreline used for this report is May 2009.
Background
Landgate and Main Roads are currently maintaining and updating ‘fit for purpose’ road
information (spatial and attributes) for their core business requirements.
Landgate are state providers of spatial data and produce various products and services that
meet the spatial consumer market in Western Australia.
Main Roads Western Australia is the state authority for roads and utilise their spatial data to
manage the State Road asset and provide support to Local Government and DEC (other
road custodians).
Both organisations are looking for opportunities to collaborate and seek ways to remove
duplicated processes, enhance the quality of road data and provide a better return on
investment to the state.
Any comments, suggested changes or modifications to this document are appreciated. All
such comments can be addressed via email to roadinfo@mainroads.wa.gov.au Tel (08)
9323 4410 or Fax (08) 9323 4629.
How to use this document
The document is divided into three main sections:
Section 1: Modelling Roads
This section provides some background on how Landgate and Main Roads model
roads.
Section 2: Road and Route Analysis
This section provides information on the analytical process used in this document.
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Section 3: Conclusion
This section provides a conclusion on the process and adds further comments for the
WALIS Road Group to consider in light of this report.
Abbreviations and Definitions
The following definitions and abbreviations are used in this document.
Routable Road Centreline Network (RRCN): Road centreline that can be used for
navigation that meets the operational requirements of government agencies.
Integrated Road Information System (IRIS): Main Roads’ corporate road information
management system.
SLK Linear Referencing: A referencing system that uses a known measured value for the
start and end point of a route and then is used to locate features on the route according to
their relative position to the whole length of the route.
Link-Node Linear Referencing: A referencing system that uses a known measured value
for the start and end node of a link and then is used to locate features on the link according
to their relative position to the length of the link.
Route: Where one or more road sections are grouped and assigned a unique number.
State Road: All highways and main roads under the control of Main Roads Western
Australia.
Local Road: All roads that are under the control of Local Governments.
Department of Environment and Conservation (DEC) Road: All roads that are under
the control of Department of Environment and Conservation.
Private Road: Any other road that is not a State, Local or DEC road.
Logical Length: The assigned measure of a road section or route such as SLK.
Spatial Length: The absolute 2D measure of a road section or route.
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SECTION 1 – Modelling Roads
Both Landgate and Main Roads centrelines are modelled and managed in different ways.
Landgate use a typical GIS model that is suitable for the creation of high end products
whereas Main Roads use a link-node model in line with road asset management principles.
Typical GIS Model
Traditional GIS logic for roads follows a concept that where the attribute of a feature is
contiguous for a section of a road, then this road section is represented by a single part
feature (road segment). Where an attribute changes along the road then a new road
segment is created.
Where;
SE = Sealed
US = Unsealed
Start of new
road section
In the Landgate example above, where the attribute of the highlighted road changes from
‘SE’ to ‘US’ (Sealed to Unsealed), then a new road segment is created. This method of
maintaining road attributes can create a large number of road segmentations.
It is useful to note that Landgates’ road attributes are generalised to minimise the number of
road segments.
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Link-Node Model
The link-node model used by Main Roads represents the same piece of road as a
continuous road section. This road section starts at the first intersection (node) north of the
area of interest and ends at the intersection (node) south of the area. Notice that another
section starts at an intersection and represents the last road section for this road.
Area of Interest
For Main Roads, road sections provide the framework by which road information is
managed and reference in a logically connected data base relationship and this represents
the physical road network.
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In the Main Roads example, the attributes of the highlighted road are stored in an
integrated road data base i.e. attributes are referenced to the road by means of linear
referencing.
0.00
Where;
0.00 = Start
3.49 = Change
3.49
A product ‘view’ of sealed or unsealed roads is created from the data base using a dynamic
segmentation process. This process segments the road sections to the view needed.
This view is not managed, just used in mapping products and refreshed when required.
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SECTION 2 – Road and Route Analysis
The following results are provided from analysis of the Landgate centreline.
Road Number
The road number is used by Main Roads to associate a road section with an agency
responsible by an ‘act’ or ‘obligation’ to manage and maintain that road. It is also used to
create routes (see Route Analysis).
The following chart compares the number of Landgate road segments without a road
number.
Number of Landgate Road Segments and Main Roads Road Sections
Notes:
1.
Main
Roads only includes State and Local Government roads that are regularly
maintained (funded or unfunded).
2. Landgate includes DEC and other private roads where responsibility may not be
clearly defined (65% of road segments not tagged).
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Route Analysis
Routes
A route can be defined as ‘one or more road sections that are grouped together and
assigned a unique number’.
Analytical Process
The following steps have been used to validate the currency of Landgate tagging and
roads found with significant differences have been excluded from further analysis.
The following steps were used to complete the analysis:






Create Landgate Routes from tagged road segments;
Prepare Length Table (Spatial Lengths + Min Max SLK’s of Main Roads Routes);
Join Table to Landgate Routes;
Eliminate ‘Out of Scope’ Routes;
Create Landgate Routes with Main Roads SLK’s;
Display ‘Main Roads’ Events on ‘Landgate’ Road Centreline; and
Step 1: Using the ArcGIS ‘Create Routes’ tool, it is possible to create routes using the
Landgate ‘MRWA_NUMBE’ field that contains the road number that uniquely
identifies each route. Roads with null ‘MRWA_NUMBE’ are excluded.
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Create Routes Results
Step 2: Use the ArcGIS ‘Frequency’ tool to create a table with spatial length,
Minimum and Maximum SLK value and Road Name for each unique road.
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Step 3: Join the table from Step 2 to the Landgate Routes created in Step 1.
Step 4: Eliminate ‘Out of Scope’ Routes.
i)
Calculate the difference in spatial length of the Main
Roads and Landgate routes.
ii)
Analyse the results and eliminate roads <> +/- 30m
length differences.
Analysis Results
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Step 5: Create new Landgate Routes with Main Roads SLK’s.
Note: Landgates ‘MRWA_NUMBE’ or Main Roads’ ‘ROAD_NO’ field can be used.
Step 6: Display ‘Main Roads’ Route Events on ‘Landgate’ Road Centreline.
Using a subset of IRIS Local Road Inventory (exclude state roads in this instance) the
following attributes are added to Landgate road centreline.
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Once a layer of events is created, export the layer to an appropriate spatial data
format. The new layer will have roads segmented as per the IRIS Local Road
Inventory data.
The picture on the right shows
the extent of Landgate road
segments tagged with road
numbers and created as routes
and then segmented to have
Main Roads stored attributes
attached.
The black roads are sealed
roads, grey are unsealed.
A ‘visual’ inspection of the
results compared to the May
2009 Landgate sealed/unsealed
road found differences.
Differences have not been
quantified in this report.
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SECTION 3 – Conclusion
This section provides a summary of the results and some conclusions and suggestions for
the WALIS Road Group.
Conclusion
1. A process could be created to semi automate the addition of IRIS data directly
onto Landgate road centreline using standard ArcGIS tools. Periodically, new
‘views’ could be provided to Landgate to overlay onto their current road centreline
to verify such items as:
 Road Width (Main Roads Source);
 Seal Information;
 Road Hierarchy;
 Road Type (Sealed, Unsealed); and
 MRWA_TYPE.
Other attributes such as LG responsibilities can also be derived (from the LG
road number).
2. The process to transfer Main Roads stored attributes to Landgates road centreline
is not a tedious task, but verifying the results against current Landgate data was
not completed as part of this exercise and could prove to require a large amount
of effort. It might be an interesting exercise (a separate project) to verify Landgate
and/or Main Roads data. It is understood that Landgates road attributes can
sometimes be generalised for the purpose of preparing cartographic products.
3. The Main Roads’ road number can be used as a key to link Main Roads attribute
data to the Landgate road centreline. The reverse may also be true. Main Roads
may be able to apply the Main Roads ‘Network Element Number’ to each
Landgate road section so that a new ‘shape’ can be uploaded into IRIS. This was
not tested in this process and could be another interesting project.
4. If updates to Landgate/Main Roads numbers are maintained, this will increase the
integrity of any transfer of attributes. Creating a change report of changes to road
numbers would benefit Landgates processing and management of Main Roads
road numbers. Automating a ‘change’ report directly from IRIS would be ideal, but
a manual semi automated process may need to be created as an interim solution.
5. It is recommended that Main Roads and Landgate complete an end to end
analysis of the differences in the way their roads a modelled to consider if what is
done is ‘best practice’. Bench marking eastern states road authorities (VicRoads)
would be of significant benefit.
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Other Issues
Digitised Direction of Roads
It can be expected that some of Landgates’ road sections are digitised in the opposite
direction than those of Main Roads. Checking the digitised direction of Landgate
roads was not tested and the impact of segments in conflicting directions is
unquantified in this analysis.
Main Roads has recently adopted, where possible, to store the spatial direction of
roads in IRIS in the direction of increasing address range.
Spatial Topology
The Landgate spatial data set provided to Main Roads did not include spatial topology
(because it is provided as a shapefile, a poor cousin to file geodatabases). Landgate
road centreline maintains spatial topology but was not essential for this exercise. The
output of this process does not maintain spatial topology.
Roads not assigned a Designated Custodian
Landgates road centreline includes roads that do have a designated custodian. A
large number of these are expected to be DEC roads, but other roads that don’t have
a custodian would be excluded from this process. The issue of roads without a
designated custodian is significant to Main Roads and covers questions about roads
being mapped that are not safe for use by the public, road accountability and possibly
opens up legal some liability issues.
Road Lengths
The use of 2D measures (spatial length) to exclude Landgate roads is a crude
method of eliminating roads from this process and did not take percentage
differences of road lengths into consideration, which I believe would result in more
Landgate roads being included in this process.
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APPENDIX A: Reference Documents
1 IRIS Road Centreline Representation Model Catalogue.
Document describes the link-node model used in Main Roads Western Australia and the
way roads a modelled spatially in IRIS.
A copy of the latest document can be sourced by contacting Daniel Grillo or please contact
roadinfo@mainroads.wa.gov.au .
2 Project Area
The following Road Information Services Project Area was used to prepare this report.



Server: \\Dacsrv02\ani\RIS\PROJECT\Geodata
Directory: YR2009
Folder: J25514
Project area and this report prepared by Senior Spatial Analyst, Daniel Grillo at Main Roads
Western Australia.
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