Abstract
Cutting-edge scalar airborne gravimeters can measure the Earth's gravity field with an accuracy of 1–2 mGal for spatial resolutions as high as 2 km (half wavelength). These specifications make gravity data from airborne systems applicable for geoid determination. Airborne gravity data must however be filtered prior to their intended applications in order to reduce the high-frequency observation noise caused mainly by aircraft dynamics. As a result, only discrete samples of the band-limited representation of the continuous gravity field can be obtained. Such gravity data can however be used successfully for accurate band-limited geoid determination. The second method of Helmert gravity reduction is considered in this contribution by studying procedures that would allow for evaluation of band-limited topographical effects on gravity and the geoid that are consistent with the relatively high accuracy and high spatial resolution of band-limited airborne gravity observations available today and in the foreseeable future. Using a 3×3 arcsec digital elevation model, values of the topographical effects are computed using the second method of Helmert reduction along selected flight lines in the Canadian Rocky Mountains. The values of the topographical effects are processed by the same low-pass filter that is applied to airborne gravity and compared to values computed by newly developed algorithms. This new approach can be used for computation of the topographical effects from a set of spherical harmonic coefficients. It results in a fast and efficient algorithm which can be used worldwide (with the exception of the polar regions) for the reduction of airborne data used for geoid determination. The next step of gravity reduction, the downward continuation, is not treated in this contribution.
Published Version
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