Global Mapper Grid

The Export Global Mapper Grid command allows the user to export any loaded elevation grid data sets to a Global Mapper Grid format file. The Global Mapper Grid format is a highly compressed elevation grid format that loads and draws very quickly and requires very little memory. If you have a choice for what format to store your gridded elevation data in, we suggest using the Global Mapper Grid format.

When selected, the command displays the Global Mapper Grid Export Options dialog which allows the user to setup the export. The dialog consists of a General options panel which allows the user to set up the grid spacing and vertical units, a Gridding panel, and an Export Bounds panel which allows the user to set up the portion of the loaded data they wish to export.

Quadrangle Name

(Optional) A descriptive name identifying the map. This is typically named by a local physical feature.

Vertical Units

Select from the following options:

  • Meters
  • Decimeters
  • Centimeters
  • Millimeters
  • Feet
  • Decifeet
  • Inches
  • Centifeet
  • Millifeet

Note: GMG files store elevation values as integers. To maintain precision in the output file, specify a small vertical unit, such as Centifeet, Millimeters, etc. When a larger unit is selected the resulting file will show a 'stair-step' effect due to the loss of precision.

Interpolate to fill small gaps in data

Any small areas with missing data will be filled in by interpolating the surrounding valid data using an IDW method. This is useful for filling small gaps between adjacent tiles or small holes in elevation data.

Generate PRJ File

A PRJ file describing the projection of the coordinates in the file will automatically be created .

Only Use Lossless Compression

Early Global Mapper exports (v15.1 and earlier) used lossy compression for GMG files. Since Global Mapper v15.2 the default is to use lossless compression.