R: Euclidean or Great Circle distance between points

spDistsN1 {sp}

R Documentation

Euclidean or Great Circle distance between points

Description

The function returns a vector of distances between a matrix of 2D points and a single 2D point, using Euclidean or Great Circle distance (WGS84 ellipsoid) methods.

Usage

spDistsN1(pts, pt, longlat = FALSE)
spDists(x, y = x, longlat = FALSE)

Arguments

`pts`	A matrix of 2D points, or a SpatialPoints or SpatialPointsDataFrame object
`pt`	A single 2D point, or a SpatialPoints or SpatialPointsDataFrame object with one point only
`x`	A matrix of n-D points with row denoting points, or a Spatial object that has a coordinates method
`y`	A matrix of n-D points with row denoting points, or a Spatial object that has a coordinates method
`longlat`	if FALSE, Euclidean distance, if TRUE Great Circle distance

Value

spDistsN1 returns a numeric vector of distances in the metric of the points if longlat=FALSE, or in kilometers if longlat=TRUE.
spDists returns a full matrix of distances in the metric of the points if longlat=FALSE, or in kilometers if longlat=TRUE; it uses spDistsN1 in case points are two-dimensional. In case of spDists(x,x), it will compute all n x n distances, not the sufficient n x (n-1).

Note

The function can also be used to find a local kilometer equivalent to a plot scaled in decimal degrees in order to draw a scale bar.

Author(s)

Roger Bivand

References

http://home.att.net/~srschmitt/script_greatcircle.html

Examples

ll <- matrix(c(5, 6, 60, 60), ncol=2)
km <- spDistsN1(ll, ll[1,], longlat=TRUE)
zapsmall(km)
utm32 <- matrix(c(276.9799, 332.7052, 6658.1572, 6655.2055), ncol=2)
spDistsN1(utm32, utm32[1,])
dg <- spDistsN1(ll, ll[1,])
dg
dg[2]/km[2]
data(meuse)
coordinates(meuse) <- c("x", "y")
res <- spDistsN1(meuse, meuse[1,])
summary(res)

[Package sp version 0.9-57 Index]