Surfer imports elevation data from GTopo30 data sets.
A GTopo30 data set consists of multiple files. The following files must exist in the same directory:
.HDR contains header information
.STX the statistics file, used to obtain zmin, zmax
.DEM contains the actual grid nodes
GTopo30 files are extremely large. Surfer can read the files, though approximately 220 MB of RAM is needed for this operation due to the grid size. You can use Grids | Resize | Extract to make the file smaller. You must have the associated .DEM, .HDR, and .STX files to use GTopo30 files in Surfer. These files are necessary for computing the X, Y, and Z limits. Some GTopo30 files contain a "no data" value of -9999 in the file. The no data value is set to zero elevation in Surfer.
Loading .HDR Files
GTopo30 .HDR files can be loaded to create a grid based map (i.e. Home | New Map | Contour) with the Open Grid dialog, or when using the functions in the Grid menu..
Import Options Dialog
No import options dialog is displayed.
Import Automation Options
No import options are available.