GeoCircle

GeoCircle[loc,r]

is a two-dimensional GeoGraphics primitive that represents a circle of radius r centered at the location loc on the surface of the Earth.

GeoCircle[loc,r,{α1,α2}]

represents a sector of a circle from bearing α1 to bearing α2.

Details

  • A geo circle with center loc and radius r is defined as the endpoints of all geodesics of length r starting from loc. Specifying bearings α1 and α2 restricts the set of geodesics.
  • The location loc can be specified either as latitude and longitude coordinates {lat,lon} in degrees, GeoPosition[], or as a named geographical Entity[].
  • The radius r can be given as a Quantity length or as a number in meters.
  • Bearings α1 and α2 are measured clockwise from true north and can be given as Quantity angles, as numbers in degrees, as DMS strings, or as named compass points like "N" or "SouthWest".
  • GeoCircle[loc] represents a geo circle centered at loc, with an automatic choice of radius.
  • GeoCircle[] is equivalent to GeoCircle[$GeoLocation].

Examples

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Basic Examples  (2)

A circle of 3000 kilometers around a geo location:

A sector of a circle over South America:

Scope  (6)

The center location of the geo circle can be specified in several ways:

The default location is the local geo position:

The geo circle radius can be specified as a Quantity object or directly in meters:

The default radius is computed automatically:

Bearings are given in degrees, clockwise with respect to true north:

Use different styles for geo circles:

Applications  (1)

Illustrate projection effects by same-area circles:

Properties & Relations  (7)

A geo circle is the set of points whose distance to the center is the radius:

The interior of a geo circle is a geo disk:

A GeoCircle object is described using coordinates and distances on the Earth, irrespective of the coordinates used in the final map. A Circle object is described using the coordinates of the final map:

It is possible to use a GeoPosition object to specify the center of the Circle object. Its radius, however, cannot be specified as a length on the surface of the Earth:

As the distance from the equator increases, geo circles look more distorted in the equirectangular projection:

A geo circle having a pole inside spans all values of longitude:

All three sides of a geo circle sector are generically curved. The radii spanning from the center are geodesics:

Even starting from bearings and , the sides are curved:

Large circles accumulating around the antipodal point, using a spherical model of the Earth:

The default reference model is an ellipsoid:

Interactive Examples  (1)

Interactively place a geo circle of fixed radius and observe how its form changes as a function of latitude:

Neat Examples  (1)

Draw approximate geo circles corresponding to the various seas and oceans of the world:

Use a different projection:

Introduced in 2014
 (10.0)