Sorry if this is not the right forum. Having a velocity grid in which a wave propagates, and given a certain spatial sampling of the grid, what kind of smoothing/interpolation should be used if the grid is to be resampled (decimated) ? In the top picture below, I have a velocity grid with a grid resolution of 5 meters. I need to decimate to 25 meters instead. The colorbar shows the velocity variation. The middle picture is the first gradient along the vertical and the bottom picture is the second gradient. Given waves with central frequency from 10Hz to 30Hz, what kind of smoothing should be applied before decimation to avoid spatial aliasing (least possible) ?