Use this cartographic calculation to convert, scale, or compare map, terrain, bearing, raster, or route quantities when the coordinate and unit conventions are explicitly known.

Height Above Ground Meters (m)

Required number input.

Focal Length Millimeters (mm)

Required number input.

Approximate vertical aerial-photo scale denominator H/f when altitude above ground and focal length use the same units. The tool evaluates the supplied inputs together and returns the named outputs below; it does not infer omitted operating conditions or change the units shown.^[1]

Denominator

The resulting denominator returned as a number.

• Map calculations depend on datum, projection, latitude, scale definition, magnetic-declination epoch, and whether distances are planar, rhumb-line, or geodesic. A compact formula cannot remove distortion or infer the missing reference system.
• Use finite inputs in the displayed units and preserve more precision than the final presentation requires. Independently verify safety-critical, financial, compliance, or production decisions.

Confirm the map datum, projection, scale, and bearing convention before applying the result. Use geodesic or GIS software with current reference data when survey-grade or navigation-critical accuracy is required.

• Ground Sample Distance Gsd

  Ground sample distance in centimetres per pixel for a nadir image, using altitude, sensor pixel pitch, and focal length.

• Ground To Map Distance

  Map distance in centimetres from ground kilometres and scale denominator N.

• Map To Ground Distance

  Ground distance in kilometres from map distance in centimetres and scale denominator N.