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)

Arguments

Value

A numeric vector of distances in the metric of the points if longlat=FALSE, or in kilometers if longlat=TRUE

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

See Also

is.projected

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]