Airborne Gravity 2010 - Geoscience Australia

Airborne Gravity 2010
Analysis of terrain corrections
The terrain corrections calculated by the supplier of the ground gravity survey data were based on
station GPS data and regional SRTM data (Coopes, 2009). As a complement to this work, a brief
investigation of terrain correction parameter settings and input elevation data sets has been carried
out (Grujic, 2010). The high resolution LiDAR DEM was used for the computation of more accurate
terrain corrections for the ‘core’ AGG area with 1-second SRTM data used to compute the effect of the
more distant terrain. The effects of altering key, user-selectable parameters within the terrain
correction modules of three commercially available software packages were investigated. A suitable
set of parameters including DTM sampling density and data extent were determined, along with the
results of an analysis of the trend of the inaccuracies associated with terrain corrections using a range
of variables.
This work indicated that there was little (mean) difference between the complete Bouguer anomaly
values at ground level corrected using the sparse ground gravity survey GPS elevation data and the
values corrected using the more comprehensively sampled LiDAR elevation data. However, there was
a significant difference between these two sets of corrections when applied to the Gzz gravity
gradiometry response at 80 m height simulated from the same ground gravity data (Figure 8).
(a) Satellite Image (b) LiDAR DEM (c) CBA up 80 m 1VD
(d) TMI (e) TEMPEST Ch.9 (f) FALCON gD
Figure 7. Comparison of various survey responses over the central gravity anomaly in the
Kauring AGG test range. The images are 1.35 km in east-west and 1.45 km in north-south extent.
FALCON, TEMPEST and TMI data were acquired from a single platform during a single test flight
of a Casa 212 aircraft operated by Fugro Airborne Surveys (Dransfield et al., 2010). Results
shown are from preliminary processing of the acquired data and positional accuracy has not been
verified.
Summary
The test site data and analyses are accessible at no charge from a dedicated website maintained by
Geoscience Australia. Other complementary datasets and analyses will be added as they become
publicly available.
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