Distance from coast

Here's a really simple example using the default low res longlat
coastline in the maps package. It should work for any coastal dataset
that can extract the raw coordinates from, though there's no attempts
at efficiency. spDistsN1 is really fast and works well for this
though, be careful to use longlat argument correctly.

library(sp)

library(maps)

## single point for a simple test
pts <- matrix(c(-88, 36), ncol = 2)

## simple map data
mp <- map("usa", plot = FALSE)

## convert coords to matrix and dump NA
xy.coast <- cbind(mp$x, mp$y)[!is.na(mp$x), ]


## container for all the nearest points matching the input
closest.points <- matrix(0, ncol = 2, nrow = nrow(pts))

for (i in 1:nrow(pts)) {
   closest.points[i, 1:2] <- xy.coast[which.min(spDistsN1(xy.coast,
pts, longlat = TRUE)), ]
}

map(mp)
points(pts)
points(closest.points)

Cheers, Mike.
On Fri, Sep 23, 2011 at 1:11 PM, Sandeep Patil

Hello does anyone know of any R -script or function which will give the
value of nearest distance from coast of a point
in USA.

I have a number of latitude and longitude values spread evenly across USA
and i want to find the nearest distance from coast for

each of these points. If not a function can anyone suggest me a strong
library for geographical data manipulation.

Thanks a lot

Sandeep

? ? ? ?[[alternative HTML version deleted]]

_______________________________________________
R-sig-Geo mailing list
R-sig-Geo at r-project.org
https://stat.ethz.ch/mailman/listinfo/r-sig-geo

Michael Sumner
Institute for Marine and Antarctic Studies, University of Tasmania
Hobart, Australia
e-mail: mdsumner at gmail.com