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Distance from coast

5 messages · Sandeep Patil, Michael Sumner, Kemp, Michael +2 more

Michael Sumner
# 
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
<sandeep.coepcivil at gmail.com> wrote:

  
    

      
      
    

  


  


      

    

    

      
      

        


  

        

      Kemp, Michael
    

    

      
      #
    

  


  

      
Hello Sandeep,

Tom Hengl has some world maps on his spatial-analyst website, one of which is a 'distance-to-the-coast' map.  He also has some example script for how to handle these maps.

See...
http://spatial-analyst.net/wiki/index.php?title=Global_datasets

Regards,
Michael


-----Original Message-----
From: r-sig-geo-bounces at r-project.org [mailto:r-sig-geo-bounces at r-project.org] On Behalf Of Sandeep Patil
Sent: Friday, September 23, 2011 5:11 AM
To: r-sig-geo at r-project.org
Subject: [R-sig-Geo] Distance from coast

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


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      Tomislav Hengl
    

    

      
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Sandeep,

You probably want to use:

http://commons.wikimedia.org/wiki/File:Dist2con.png

*I had some problems automatic the processing with R+SAGA (will try to
update the maps/scripts soon), but this is probably what you are looking
for.

The geotifs are at:

http://spatial-analyst.net/worldmaps/

*we are in process of migrating to www.worldgrids.org which will include
both data and the geo-services.

cheers,

T. Hengl
http://www.wewur.wur.nl/popups/vcard.aspx?id=HENGL001