Geodetic Computations

Document No:  D12#434768
Revision:  6
Date amended:  15-Nov-2019
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 Rod Stone  by e-mail or on ph. (08) 9323-6381.

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  13-Jun-2001 
 2 All  Ownership changed. 20-Jun-2006
 2A Header Contact Person changed. 05-Mar-2009
​3 ​All ​Content Clean-up ​06-Feb-2013
​4 ​Header ​Document Number Changed ​16-Jun-2014
​4A​Header​Guideline Introduction Amended​14-May-2015
​5​All​Guideline Review​10-May-2017
​6​Header​Updated contact​15-Nov-2019

Table of Content


The Senior Geodetic Surveyor can provide advice on geodetic computations and other survey computations for your project requirements.  Below are the most common transformations computed:

AMG 84 to GDA 94:  This transformation is used to convert corporate data sets (e.g. road centrelines, material reserves) into the new National Co-ordinate System.  Please refer to the policy on Co-ordinate Systems for more information on this transformation and the various methods of transformation.

GDA 94/AMG 84 to Project Zone:  All designs and set out for Main Roads Projects are completed on Main Roads WA approved Project Zones.  These Project Zones allow for calculations and set out work to be completed without the curvature of the Earth being factored in.

Easting/Northing to Latitude/Longitude:  This calculation is used to change position on the earth to be identified from metres to degrees, minutes and seconds and vice versa.

Geoid/Spheroid Separation:  This calculation is used to convert GPS measured heights into useable and identifiable AHD heights.

Least Square Adjustment Review:  All Main Roads WA control networks are computed via a Least Square adjustment technique which proportions error out through the control network.  The review will ensure there is adequate redundancy within the survey network and the adjustment computed is correct.

Please contact the Senior Geodetic Surveyor for information regarding the above computations or other survey computation requirements.