When a gridded DEM is specified as a deliverable, it must be tested to ensure it meets required accuracies even when a TIN with a “Tested to Meet” accuracy statement is used as the DEM source. This is because generalization or smoothing processes employed during DEM interpolation may degrade the elevation surface. If a gridded DEM is to be tested, surface elevations at the checkpoint locations can be interpolated using a suitable interpolation scheme.