# perimeter: Compute the perimeter of a longitude/latitude polygon In geosphere: Spherical Trigonometry

## Description

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

## Usage

 ```1 2 3 4 5 6 7 8``` ```## 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. https://dx.doi.org/10.1007/s00190-012-0578-z. Addenda: http://geographiclib.sf.net/geod-addenda.html. Also see http://geographiclib.sourceforge.net/

` areaPolygon, centroid `

## Examples

 ```1 2``` ```xy <- rbind(c(-180,-20), c(-140,55), c(10, 0), c(-140,-60), c(-180,-20)) perimeter(xy) ```

### Example output

```Loading required package: sp
[1] 40775666
```

geosphere documentation built on July 21, 2018, 3 p.m.