Rapid gravity and gravity gradiometry terrain correction via adaptive quadtree mesh discretization

We present a method for modeling the terrain response in gravity and gravity gradiometry surveys utilizing an adaptive quadtree mesh discretization. The data-dependent method is tailored to provide rapid and accurate spatial terrain corrections for ground or draped airborne surveys. The surface used in the modeling of terrain effect at each datum is discretized automatically to the largest cell size that will yield the desired accuracy, resulting in much faster modeling than fullresolution calculations. The largest cell sizes within the model occur in areas of minimal correction and at large distances away from the data location. We show synthetic and field examples for proof of concept. The adaptive quadtree method reduces the computational cost of the field example by performing 99.7% fewer calculations than the full model would require while retaining an accuracy of one Eötvös for the gradient data, and runs in 0.9% of the time for the gravity field terrain corrections compared with a commercial software package.