Land-sea mask data are represented as values 0 and 1. If the land-sea mask value of a neighbouring input point differs from the grid point being generated, the weight of the input point is reduced to modify its effect on the interpolation. The scaling factor currently applied is 0.2.
By default, ECMWF surface data in GRIB format are interpolated using a land-sea mask. This behaviour can be changed by calls to INTIN.