perimeter {geosphere}

Compute the perimeter of a longitude/latitude polygon

Description

Compute the perimeter of a polygon (or the length of a line) with longitude/latitude coordinates, on an ellipsoid (WGS84 by default)

Usage

## S4 method for signature 'matrix'
perimeter(x, a=6378137, f=1/298.257223563, ...)

## S4 method for signature 'SpatialPolygons'
perimeter(x, a=6378137, f=1/298.257223563, ...)

## S4 method for signature 'SpatialLines'
perimeter(x, a=6378137, f=1/298.257223563, ...)

Arguments

x

Longitude/latitude of the points forming a polygon or line; Must be a matrix of 2 columns (first one is longitude, second is latitude) or a SpatialPolygons* or SpatialLines* object

a

major (equatorial) radius of the ellipsoid. The default value is for WGS84

f

ellipsoid flattening. The default value is for WGS84

...

Additional arguments. None implemented

Value

Numeric. The perimeter or length in m.

Author(s)

This function calls GeographicLib code by C.F.F. Karney

References

C.F.F. Karney, 2013. Algorithms for geodesics, J. Geodesy 87: 43-55. doi:10.1007/s00190-012-0578-z. Addenda: https://geographiclib.sourceforge.io/geod-addenda.html. Also see https://geographiclib.sourceforge.io/

See Also

areaPolygon, centroid

Examples

xy <- rbind(c(-180,-20), c(-140,55), c(10, 0), c(-140,-60), c(-180,-20))
perimeter(xy)