Name

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GEO_DIST

Purpose

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This function returns the great circle distance (in km) between
two geographical points.

Category

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Geographical

Calling Sequence

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Result = GEO_DIST( Longitude1, Latitude1, Longitude2, Latitude2 )

Inputs

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Longitude1: The scalar longitude, of type floating point, of
the first point. North is positive.
Latitude1: The scalar latitude, of type floating point, of the
first point. East is positive.
Longitude2: The scalar or vector longitude(s), of type floating
point, of the second point(s). North is positive.
Latitude2: The scalar or vector latitude(s), of type floating
point, of the second point(s). East is positive.

Keyword Parameters

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SINGLE: Forces the calculation to be performed using single-
precision arithmetic (default is double).

Outputs

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Result: Returns the great circle distance between Point 1 and
Point(s) 2.

Uses

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CONSTANTS.pro

Procedure

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The function uses the Haversine formula to calculate the
arclength between the points.

Example

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Calculate the distance between Ottawa, ON (45.25N, 75.43W) and
Victoria, BC (48.25N, 123.22W).
results = geo_dist( -75.43, 45.25, -123.22, 48.25 )

Modification History

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  Written by: Daithi A. Stone (stoned@uvic.ca), 2000-06-29.
Modified: DAS, 2000-07-06 (removed LENGTH.pro, added
DIMENSION.pro).
Modified: DAS, 2000-07-24 (added Degrad constant).
Modified: DAS, 2000-08-17 (coverted from Cosine to Haversine
Haversine formula, added SINGLE keyword).
Modified: DAS, 2002-08-12 (complies with CONSTANTS.pro revision)