Advances in Strapdown Airborne Gravimetry for Geodetic Applications
21/09/2016 | 08:45 | Session 4: On the ground and airborne gravimetry
Author(s): David Becker, Arne V. Olesen, J. Emil Nielsen, Matthias Becker and Rene Forsberg
David Becker, Arne V. Olesen, J. Emil Nielsen, Matthias Becker and Rene Forsberg
For twenty years, stabilised-platform spring-gravimeters have been the predominant instrumentation for geodetic airborne gravimetry. As an alternative concept, strapdown airborne gravimetry (SAG) uses a strapdown inertial measurement unit (IMU) as gravimeter. Compared to stable-platform gravimeters, off-the-shelf navigation-grade IMUs are commonly smaller, less expensive, and easier to operate. While SAG could be shown to provide results at similar or even superior precision for the shorter wavelengths of the gravity field (up to tens of kilometres), SAG was commonly found to be rather inaccurate in the longer wavelengths, thereby preventing its stand-alone use for the local geoid determination.
Results of recent aerogravity campaigns are presented, showing that a thermal calibration of the accelerometers enables full-spectrum SAG at the 1-mGal level (non-adjusted). A comparison against a combined GRACE/GOCE global gravity model confirms the considerable reduction of long-term drifts by using the thermal accelerometer correction. Further, side-by-side comparisons between SAG (iMAR RQH-1003) and stabilised-platform gravimetry (LaCoste and Romberg S-type spring gravimeter) are presented, indicating a higher stability of SAG during strong turbulence, and also a higher spatial resolution.
The enormous potential of stand-alone SAG for the local geoid determination is briefly discussed with respect to cost-efficiency, allowing an autonomous data collection on small aircraft, and operational flexibility, allowing the gravity determination during gradual altitude changes (drape flying).