The “Clip to input area” will clip a grid back to the area covered by the input data. You would only
use this when you create a grid using data which is in an irregular shape (i.e. not square) and the
gridding method (eg. triangulation) has interpolated over large empty gaps.

When you enter a Near or Far value the grid over the empty spaces is clipped back to the extents
of the data. If you enter a high Near number, areas closer to the grid will be clipped back to the
input data extents while retaining the interpolated areas over large gaps. Alternatively, a high Far
number should remove the interpolated gridded areas over the large gaps along with any extreme
outlying data points back to the extents of the input grid.