Improvements to regional geoid modelling using airborne vector gravimetry

Airborne gravimetry conventionally measures only the vertical component of the gravity vector (scalar gravity), although modern airborne systems can now recover the full three-dimensional gravity vector. This study demonstrates two improvements to regional geoid modelling from using the full airborne gravity vector instead of the vertical component alone: (1) higher external geoid accuracy, and (2) the ability to widen flight-line spacing without loss of geoid accuracy. To quantify the improvements, we use airborne gravity vector data from New South Wales (NSW), Australia, to compute geoid models with the one-step integration method in Helmert space, combining the long-wavelength gravity signals from an Earth Gravitational Model (EGM) with short-wavelength signals recovered from the airborne data. Three input configurations used to compute geoid models include: (1) vertical component only, (2) horizontal components only, and (3) the full 3D gravity vector, each validated against independent GNSS/levelling geoid heights (i.e., external accuracy). At the original NSW flight-line spacing, using the full gravity vector (vertical plus horizontal components) improves the geoid external accuracy by 21% relative to using the vertical component alone. At progressively widened line spacings from 2 to 5 km, the full gravity vector consistently improves geoid external accuracy by approximately 44% over the vertical component alone, with the benefit becoming more pronounced at wider spacings. Most significantly, vector gravimetry enables wider line spacings across all tested configurations without loss of geoid accuracy. For example, vector gravity at ~4.5 km line spacing matches the geoid accuracy of scalar gravimetry at ~2.2 km; meaning that, in our test case, incorporating horizontal components can double the permissible flight-line spacing without sacrificing accuracy, directly reducing the cost and flight time of airborne gravimetry surveys.