The information below is intended to reflect the preferred practice of Main Roads Western Australia ("Main Roads"). Main Roads reserves the right to update this information at any time without notice. If you have any questions or comments please contact Nathan Miller by e-mail or on ph (08) 9323-4669.
To the extent permitted by law, Main Roads, its employees, agents, authors and contributors are not liable for any loss resulting from any action taken or reliance made by you on the information herein displayed.
Edited Mapping Standard Link
Each survey method has its advantages and disadvantages and in broad brush terms from Main Roads perspective are suitable for the following work:
Remotely sensed data is generally used for mapping wide corridors (up to 2km) or large block areas for planning and preliminary road design. In some cases it can be suitable for final design in rural areas or urban areas where the final level is not critical. This method requires minimal entry onto land causing little disruption to land owners. On a per kilometre rate, for covering large areas, it is generally the cheapest method but sacrifices accuracy to some degree. Engineering topographic surveys are performed to produce DTM's on small areas or corridors which are fixed or known (less than 200m) and is used as a basis for final design. This method is generally the most accurate and is ideal for final design where final level and position is critical. It is also usually the most expensive. Global Positioning System (GPS) is a satellite based navigation system developed by the United States Department of Defence. It is widely used for civilian navigation and positioning, surveying and scientific applications. It has a wide range of applications and is generally used in combination with the above surveying methods. GPS does however does have some limitations with data capture specifically with height. (GPS application and additional information)
The different methods noted above are not restricted to performing only what is stated in each method. They can be used in various combinations or phases of a project to meet required outcomes. For instance, Engineering surveys can position survey control as accurately as GPS methods, or a combination of Mapping and Engineering Survey can be used to produce suitable DTM's for final design. The main difference between the survey methods stated above is cost, time and accuracy. These all vary due to the requirements of each individual project.
The remainder of this page specialises in remotely sensed mapping (ie from aerial photography - photogrammetry or satellite imagery) and the integration of mapping data from other sources. (Engineering and Geodetic).
Existing digital mapping can be sourced through the Data Manager or the Senior Mapping Surveyor. The accuracy and contour interval of these maps vary and a clear idea of project requirements must be known.
Main Roads maintains a number of standard mapping briefs to assist project managers with the delivery and capture of this mapping. Project specific requirements and a list of mapping consultants can be obtained from the Senior Mapping Surveyor to ensure data is captured to Main Roads standards. Advice can also be sought on cost, timing and key deliverable's.
Mapping policies are also an integral part of requesting mapping and should be used in conjunction with Main Roads standards. Policies may effect how work is performed or received by Main Roads.