Sparse data acquisition and its influence on imaging

For the detection of buried objects using GFR technology, it is often necessary to acquire data over a two-dimensional area. To obtain a three-dimensional image of the subsurface using such a C-scan we have to apply three-dimensional imaging methods. To avoid artifacts in the image we have to sample sufficiently in both inline and crossline direction. Generally this results in a quadratic increase of the number of data compared to acquisition along a line. Consequently, the acquisition time and costs are increased as well. Often a practical compromise is chosen such that inline spacing is kept small, but the crossline spacing is increased for faster acquisition. We have investigated the influence of the spatial acquisition geometry on the final image that is obtained after three-dimensional imaging. For that purpose, we have modeled the back scattering by a point scatterer created by the radiation of a dipole antenna on a half-space. By using a three-dimensional diffraction stack as imaging algorithm for different acquisition geometries we can observe the acquisition footprint in the image. We conclude that the crossline spacing only weakly influences the resolution in the inline direction, especially for lines at zero crossline offset to objects.