pointDistance: Distance between points

Description

Calculate the geographic distance between two points on a sphere (type='GreatCircle') or on a plane (type='Euclidean').

Usage

pointDistance(point1, point2, type='Euclidean', ...)

Arguments

point1

x and y coordinate of first (set of) point(s), either as c(x, y) or as matrix(ncol=2) in degrees for great-circle distance, in meters (or similar) for Euclidean

point2

x and y coordinate of second (set of) second point(s). Like point1. If point1 and point2 are both matrices they should have the same number of rows

type

either 'Euclidean' or 'GreatCircle'

...

Additional arguments. Can be used to set the radius, r, of the world (modeled as a sphere), in meters, for use in Great Circle Distance. Default is r=6378137

Value

A single value or a vector of values giving the distance in meters (great-circle distance) or map-units (for instance, meters in the case of UTM)

Details

A sphere is an approximation for the earth (a spheroid) and type='Greatcircle' can thus be used with geographic coordinates (latitude & longitude). You can use type='Euclidean' for coordinates of a map projection such as UTM (but note that in some projections distance is distorted).

Examples

Run this code

a <- cbind(c(1,5,55,31),c(3,7,20,22))
   b <- cbind(c(4,2,8,65),c(50,-90,20,32))   

   pointDistance(c(0, 0), c(1, 1), type='Euclidean')
   pointDistance(c(0, 0), c(1, 1), type='GreatCircle')
   pointDistance(c(0, 0), a, type='GreatCircle')
   pointDistance(a, b, type='GreatCircle')
   
   #Make a distance matrix (dist object)
   dst <- matrix(nrow=4,ncol=4)
   for (i in 1:4){dst[,i] <- pointDistance(a[i,],a, type='GreatCircle')}
   dst <- as.dist(dst)
   
   #Now the same, but avoiding the loop
   dst <- pointDistance(a[rep(1:4,times=4),],a[rep(1:4,each=4),], type='GreatCircle')
   dst <- as.dist(matrix(dst,ncol=4))

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