What are they?
- Geoid models are used by land surveyors and airborne contractors to convert any GPS-derived elevations to AHD elevations
- Since 2011 Australia officially uses a new geoid model – AUSGeoid09
- AUSGeoid09 is significantly more accurate than its predecessor AUSGeoid98 (±0.05m compared to ±0.5m)
- The result is offsets of up to 0.5m between the two (see figure below)
Why is this important for flood studies?
Older (pre-2011) datasets may have been corrected to AHD using the older AUSGeoid98 model, whilst post-2011 datasets have probably been corrected using the newer AUSGeoid09 model. This could result in a systematic elevation offset between old and new datasets if being used on the same project.
If you suspect this to be an issue on one of your projects or you would like more information how Water Technology can help your organisation with GIS mapping, please contact us either on 03 8526 0800 or email: .