geosphere (version 1.3-13)

dist2Line: Distance between points and lines or the border of polygons.

Description

The shortest distance between points and polylines or polygons.

Usage

dist2Line(p, line, distfun=distHaversine)

Arguments

p

longitude/latitude of point(s). Can be a vector of two numbers, a matrix of 2 columns (first one is longitude, second is latitude) or a SpatialPoints* object

line

longitude/latitude of line as a matrix of 2 columns (first one is longitude, second is latitude) or a SpatialLines* or SpatialPolygons* object

distfun

A distance function, such as distHaversine

Value

• matrix with distance and lon/lat of the nearest point on the line. Distance is in the same unit as r in the distfun(default is meters). If line is a Spatial* object, the ID (index) of (one of) the nearest objects is also returned. Thus if the objects are polygons and the point is inside a polygon the function may return the ID of a neighboring polygon that shares the nearest border. You can use the over functions in packages sp or rgeos for point-in-polygon queries.

See Also

dist2gc, alongTrackDistance

Examples

line <- rbind(c(-180,-20), c(-150,-10), c(-140,55), c(10, 0), c(-140,-60))
pnts <- rbind(c(-170,0), c(-75,0), c(-70,-10), c(-80,20), c(-100,-50), 
         c(-100,-60), c(-100,-40), c(-100,-20), c(-100,-10), c(-100,0))
d = dist2Line(pnts, line)
plot( makeLine(line), type='l')
points(line)
points(pnts, col='blue', pch=20)
points(d[,2], d[,3], col='red', pch='x')
for (i in 1:nrow(d)) lines(gcIntermediate(pnts[i,], d[i,2:3], 10), lwd=2)