[R-sig-Geo] shortest distance from points to polylines

Kamran Safi ksafi at orn.mpg.de
Wed May 20 12:41:08 CEST 2009

Hi Pilar,

I had to do the same recently and find the shortest distance from a 
point to a line. The solution I chose was to point sample the line and 
then find the nearest point from the sample. You can work with 
spsample() and spDistN1().
Here's the bit that did it for me (it can be written shorter):

tempPoints <- spsample(<Line>, n=samplesize, type="regular")  # sample 
it at an interval
tempPoints<- as.matrix(as.data.frame(tempPoints))   #get their coordinates
dists <- as.data.frame(cbind(Longitude=tempPoints[,1], 
Latitude=tempPoints[,2], distance=spDistsN1(as.matrix(tempPoints), 
c(<POF_Long>, <POF_Lat>), longlat=FALSE)))  #calculate the distances of 
the point of interest from the sample points on the segment
dists <- dists[order(dists$distance),]  #sort by distance
P1 <- dists[1,c("Longitude", "Latitude")] # get the closest point on the 
segment to the watch site



Pilar Tugores Ferra wrote:
> Hi list!
> I need computing shortest distance from points to a polyline layer (coast line).
> I've been searching all the morning a function in R that can do this but couldn't find anything! 
> Is there any R function that do this? Or can anybody give me some hint about how it could be done?
> Kind regards!
> Pilar
> Mª Pilar Tugores Ferrà
> PhD Student
> Instituto Español de Oceanografía
> Centro Oceanográfico de Baleares
> Muelle de Poniente s/n
> 07015 Palma de Mallorca
> Baleares, España
> Telf.: (34) 971 401561
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