Modelling the influence of terraced landforms to the earth’s gravity field

Abstract

Medium resolution (1–3 arc-min) gravity anomaly grids do not reflect reality very accurately over terraced landforms, which in turn may affect the uncertainty of subsequent geoid modelling. This inaccuracy is due to many factors. The gravimetric datasets used in the gridding of gravity field models have a varying accuracy and coverage, especially in terraced and coastal areas. Further, the resolution of the terrain model used in the modelling of anomaly grids is usually too low to capture the complete gravimetric attraction of terraced landforms. Since the values of free-air anomalies are strongly correlated with terrain heights, it is difficult to model the gridded surface over terraced landforms. Depending on the quality of existing gravity data and terrain height models, different procedures should be used. In the case of a terraced area that is densely covered by gravity data, if an accurate terrain model exists, free-air anomaly grids should be calculated on high resolution (6″ × 12″) and using Bouguer anomaly values on grid nodes. If gridding is proceeded without Bouguer anomalies, triangulation based gridding methods should be preferred.