Aerial Surveys

Document No:  D13#41981
 
Revision:  5
 
Date amended:  04-Feb-2013

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.

 

Revision Register

Ed/Version Number Clause Number Description of Revision Date

1

All

Guideline Developed. 05-Jun-2003

2

All

Change of Page Name. 01-Jun-2003

3

5

Mapping Standard Revised. 14-Mar-2012

4

5

Editorial change. 17-Mar-2012
​5 ​All

​Edited Mapping Standard Link

Content Cleanup

​04-Feb-2013

Table of Content


1 General

Digital mapping is used within Main Roads for planning, route analysis and final design.  To understand what type of mapping you require to complete your project in the most economical way you must have a understanding of the different methods that mapping can be captured.

2 Methods of Digital Mapping

Mapping within Main Roads is derived from one of three survey methods in order to produce Digital Terrain Models (DTM's) for planning and design for Main Roads.  These are: Remotely sensed data (Mapping section) - this is information that is captured remotely and then processed ie photogrammetric mapping from aerial photography or satellite imagery.  This method of survey is suitable for producing mapping and imagery for planning or design.

Engineering topographic surveys (Engineering Surveys) - some examples of this method of survey are radiate pickups, set out surveys, waterway surveys, major and minor control surveys or any work that involves a ground survey using a total station.

Global Positioning System (GPS) surveys (Geodetic section)  - utilising GPS to locate position for control points and detail surveys.

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). 


3 Existing Digital Mapping Availability

Within the Survey and Mapping section there is a number of digital mapping data sets available.  These all have varying coverage, vintages and accuracy.  Generally, this mapping consists of: Project specific mapping - created from past Main Roads projects.

Digital mapping series from Department of Land Administration (DOLA) consisting of 1:2000 to 1:100000 map sheets depending on location.


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.

4 Project Specific Digital Mapping

Should it be determined that digital mapping is the most cost effective, suitable product to meet your project needs, project specific mapping can be obtained.

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.

5 Mapping Standards

To ensure that all mapping is uniform and meets required accuracy, a set of mapping standards have been developed that apply to newly captured mapping within Main Roads.  These standards specify accuracy and digital requirements of all mapping data. 

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.


6 Digital Data Verification and Audit

An important component of the capture of project specific digital mapping is to ensure that data conforms to project requirements.   The Senior Mapping Surveyor can provide advice on audit methods to ensure that there is a high confidence on the accuracy of project specific mapping.  It is recommended that audit verification is included with the mapping contract.

 

7 Time and Cost

It is also important to consider that a realistic lead time has been planned and sufficient funding has been allocated to create project specific mapping.  Time and cost varies between project size and requirements.