Airborne Gravity 2010 - Geoscience Australia

Airborne Gravity 2010
Performance of the gravimeter based on results from three different gravimeters on two different
aircraft was improved over specifications by an average of 30%. All new and existing GT-1A and GT-
2A gravimeters have the new shock mount and side panels installed.
(a)
(b)
Figure 7. Repeat line data profiles collected with GT-1A SN005 in Geraldton, Australia, in
November 2006. (a) From Table 2, the average RMS on the 6 passes is seen to be 0.44 mGal
with a 100 second filter. (b) The same data processed with an 85 second filter produced an
average RMS of 0.55 mGal.
Analysis of the May 2007 LDEO test flight data
Introduction
In May 2007, at the invitation of the Lamont Doherty Earth Observatory (LDEO) of Columbia
University, we installed a GT-1A gravimeter in a Twin Otter aircraft in Alberta. LDEO also installed an
AIRGrav system (Sander et al., 2004; Sander and Ferguson, 2010) in the same aircraft for
performance comparison purposes. They flew a series of repeat line passes in the Turner Valley area
southwest of Calgary and published the results in the form of a poster (Figure 8) (Studinger et al.,
2007) and in an article (Studinger et al., 2008). In the following, we provide an alternate analysis of the
GT-1A data. The performance results of the AIRGrav gravimeter are quoted directly from the poster.
The GT-1A data for some of the passes should have been rejected. The raw data channel for the
GT-1A has a dynamic range limited to ± 0.5 g on the coarse channel when measured with a bandwidth
of 150 Hz. If flight turbulence conditions exceed this value, the limits of the coarse channel can be
exceeded which leads to saturation of the electronics. This causes the post-processing software to
automatically decrease the effective bandwidth of the data. If too many coarse channel saturations
occur, the line must be rejected and re-flown.
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