AUSPOS - Understanding the Results
- Question 4.1 - How do I read the processing report?
- Question 4.2 - What part of the report should I check carefully?
- Question 4.3 - Why are GDA94 values different from the ‘original’ GDA94 values?
- Question 4.4 - What are the “Derived AHD” and “Derived Above Geoid” heights?
- Question 4.5 - The report provides GDA94 and ITRF coordinates, but what about WGS84 coordinates?
- Further information
The processing report is provided in Adobe PDF format.
It is recommended that you read the whole report thoroughly to familiarise yourself with the AUSPOS process. The important quality statistics related to your processing job are located in Section 5 of the AUSPOS Report. This includes information such as the Coordinate Precision and Ambiguity Resolution.
You may notice a difference between the 'original' GDA94 coordinates and the AUSPOS derived GDA94 coordinates. These differences could be the result of errors in the original GDA94 GPS coordinates and / or modelling errors in the transformation process (from ITRF to GDA94).
In the GDA94 section of the AUSPOS report, the user is supplied with a 'Derived AHD’ height. This is a height computed using AUSGeoid09. The offset between the ellipsoid and AHD is computed using Geoscience Australia’s AUSGeoid09 product and subtracted from the ellipsoidal height providing the user with a Derived AHD height. In most cases this is accurate to within 0.03 m. For more information, refer to the AUSGeoid09 page.
In the ITRF section of the AUSPOS report, the user is supplied with a ‘Derived Above Geoid’ height. This is a height relative to the Earth Geopotential Model 2008 (EGM2008). More information on the EGM2008 geoid can be found here .
ITRF and WGS84 are generally considered to be equivalent (to within 0.1 m).
- WGS84 and the Geocentric Datum of Australia 1994 [ PDF 108KB]
- ITRF and WGS84
- See "Malys, S. and J. Slater, 1994, Maintenance and Enhancement of the World Geodetic System 1984, Presented at The Institute of Navigation, ION GPS 94, Salt Lake City, Utah, September".
Topic contact: firstname.lastname@example.org Last updated: May 8, 2013