gives the actual geo area corresponding to a unit area on the geo grid obtained with projection proj, evaluated in the limit of small geo regions around location loc.

Details and Options

  • GeoGridUnitArea combines the global nominal scale (the shrinking factor of the geo model to the reference model of the map, traditionally denoted as 1:125000 and similar) and the local distortion of area induced by the geo projection.
  • The result of GeoGridUnitArea[] corresponds to a ratio of Quantity geo areas on the geo model (of Earth or any other body) and dimensionless areas of the projected geo grid.
  • A geo projection can be given as a named projection "proj" with default parameters or as {"proj",params}, where "proj" is any of the entities of GeoProjectionData and params are parameter rules like "StandardParallels"->{33,60}. GeoProjectionData["proj"] gives the default values of the parameters for the projection "proj".
  • The location loc can be given as a coordinate pair {lat,lon} in degrees, a geo position object like GeoPosition[] or GeoGridPosition[] or as a geo entity Entity[].
  • GeoGridUnitArea threads over its location and direction arguments.
  • Possible options of GeoGridUnitArea include:
  • GeoModelAutomaticmodel of Earth or a celestial body
    UnitSystem$UnitSystemunit system to use in the result


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Basic Examples  (1)

Compute the geo grid unit area induced by the Mercator projection at the location of the Eiffel Tower:

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A small square of side length 0.01 in projected coordinates has the following area:

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Draw the square:

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Scope  (5)

Options  (2)

Applications  (3)

Properties & Relations  (3)

Possible Issues  (1)

Introduced in 2019