When using Grids | Resize | Mosaic, Surfer uses resampling methods to assign data values in the new grid. For each grid node location in the output grid (X, Y) the Z value is located in the set of input grids. The Z value is computed according to the specified resample method.
Note that all resample methods are exact interpolators - that is, if the X, Y location falls exactly on a grid node, the grid node’s Z value is returned. If more than one grid can supply a Z value at the specified X, Y position, they are combined according to the specified Overlap Method.
The resampling methods do not extrapolate outside the grid limits. This means that NoData nodes may be inserted between adjacent input grids if the input grids to not each include the common boundary.
The Nearest Neighbor method applies the closest grid node value on the original grid to the grid node value in the new grid. When the original grid and the new grid differ in size, more than one original node may be applied to the new grid and some original grid cells may not be applied to the new grid.
The Nearest Neighbor method is the fastest resampling method, though it can result in distorted output if the original grid and new grid differ in size.
The Bilinear Interpolation method uses a weighted average of four nodes in the original grid and applies this to the new grid node. The new grid is smoothed compared to the original grid.
The Cubic Convolution method uses a weighted average of 16 nodes in the original grid and applies this to the new grid. The new grid is smoother than the original grid. This method is best for continuous data. This is the slowest resampling method, but it results in a sharper grid than the Bilinear Interpolation or the Nearest Neighbor methods.