Golden Software Grid .GRD File Description
Surfer imports and exports two-dimensional uniform lattices (elevation grids) in the Surfer Grid file format. Both ASCII and binary variants are supported.
Files with the .GRD extension are Surfer grid files. To preserve faulting information and to use double precision values in Surfer, be sure to save the grid in the Surfer 7 format. If you need to use a grid in Surfer 5 or Surfer 6, save the grid as Surfer 6 Text .GRD or Surfer 6 Binary .GRD. Keep in mind that these two formats do not retain fault information or double precision values.