BMP files are image files that contain RGB bands. Global Mapper automatically recognizes BMP files with a *.BMP extension. BMP files can also be loaded directly out of a zip directory with the following extensions: *.tar.gz, *.tgz, *.zip, *.7z . BMP files do not contain embedded spatial information. A *.prj file in the same directory of the same name will be recognized as projection information. For more information see:

Loading Rasters of Unknown Type (elevation or imagery)

Loading Files with Unknown Projection


The Export BMP command allows the user to export any loaded raster, vector, and elevation grid data sets to a 24-bit RGB BMP file.

When selected, the command displays the BMP Export Options dialog which allows the user to setup the export. The dialog consists of a General options panel that lets the user set up the pixel spacing, a Tiling panel, and an Export Bounds panel that lets the user set up the portion of the loaded data they wish to export.

Sample Spacing

The Sample Spacing section allows the user to select the grid spacing to use when generating the file. The default value is the average of the grid spacings of all the currently loaded raster and elevation overlays.

If the Always Generate Square Pixels option is checked, the smaller of the specified x and y resolutions will be used for both the x and y resolution.

Selecting Always Generate Square Pixels ensures that the resultant image file will look good even in software that is not able to deal with pixels that aren't square.

To specify the spacing in units other than those of the currently selected view/ export projection, press the Click Here to Calculate Spacing in Other Units button.

Specify the X and Y spacing of the output pixels in any of the selected units. These pixel dimensions will be translated into the units of the display projection during export. The Use Current Screen Pixel Size button will update the X and Y values to the dimensions of the map display. Use Last Exported Sample Spacing will update the X and Y values to the most recent export resolution.

Band Setup for Raster Imagery Exports

  • Default RGB Layout - This option generates a BMP file with three 8-bit bands of data.

  • Grayscale - This option generates a BMP file in grayscale, with one 8-bit band of data.

  • Multiband - This option generates a raster BMP file with 1 or more bands of data at either 8-, 16-, or 32-bits per band of data. This option is very useful when working with multi-spectral imagery with more than 3 bands of data, such as RGBI, Landsat imagery, or data sets with more than 8 bits per color channel. After selecting this option, additional dialogs will be open, to set up the multi-band export by choosing the input sources for each band in the output image.


When generating a 256 color (8-bits per pixel) BMP, it is necessary to select a palette that indicates which 256 colors will be used to describe the image being exported.

The following palette choices are available:

When converting from an existing palette image, the new image will be assigned the palette index (PAX IDX) of the closest matching RGB value in the new palette.

Metadata File Formats to Generate

A range of accompanying metadata files can be generated upon export, to preserve spatial information that may not be contained in the export itself. Choose from the following Metadata file formats:

  • World File (.bpw)
  • PRJ (Projection)File
  • ESRI .aux.xml Projection File
  • ERS (ERMapper Header) File
  • TAB (MapInfo) File
  • MAP (OziExplorer) File
  • MCF (ublox Position) File
  • TXT (Text) Metadata

Save map Layout (Scale/Margins/Grid/Legend/etc.)

Selecting thisoption will save any Layout information that is currently visible (like a Scale bar or Elevation Legend) as part of the BMP file as well.

Save Vector Data if Displayed

If any vector data is also currently selected in the Overlay Control center, checking this option will save that data as part of the BMP export file.

Interpolate to Fill Small Gaps in Data

This option specifies whether or not any small gaps in the elevation or raster file being exported will be filled by interpolating between nearby known values.

Tiling Panel

Export Bounds

Format Updates

Below is a summary of recent changes to format support:

20.1 update