Re: [R-sig-eco] How to calculate geographical coordinates of sampling points following (by bearing and distance) a georeferenced one?
Trigonometry will work for projected coordinate systems like UTM:
Try this:
# number of points
n = 30
# reference location
ref.pt = cbind(1,2)
# generate some random directions
# This can be your list of your bearings converted to radians
dir - runif(n,0,2*pi )
# generate some random distances
# This can be your list of distances in map units (e.g. m)
dist - runif(n,0.5,10)
#empty matrix for coordinates
coords.mat = cbind(rep(0,n),rep(0,n))
#using trigonometry to calculate object location
for (i in 1:n){
coords.mat[i,1] = ref.pt[1]+(sin(dir[i])*dist[i])
coords.mat[i,2] = ref.pt[2]+(cos(dir[i])*dist[i])
}
plot (coords.mat)
points(ref.pt,col=2)
Best,
Tammy
On Wed, Apr 4, 2012 at 11:02 PM, Ivailo ubuntero.9...@gmail.com wrote:
Der fellow R-users,
I have several sampling sites and in each site the starting plot
(i.e. the first one that have been sampled) is georeferenced with a
GPS but the following ones are just described by their distance and
bearing in relation to the previous one.
Is there a quick way to calculate (by using some of the spatial
R-packages) the geographic coordinates of the sapling plots at each
location that have not been explicitly georeferenced?
Cheers,
Ivailo
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Re: [R-sig-eco] adehabitat - data projection
Hi Danielle, I just got the following instructions and code from a local R expert. I haven't tested it, but I think you can just switch the +proj=lonlat and +proj=utm +zone=XX +north to go from longlat to UTM. One note, though. I'm not sure how spTransform from the rgdal package handles the datum. Shifting from WGS84 (I'm assuming these are GPS longlats) to NAD83 (which all of your other GIS data are likely projected as) is not straightforward. Knowing the datum is important if you are to do any overlay analysis or raster extraction with your data. Dispite the recent display functionality of GIS software, the extract tools only reliably work on data of the same projection. 1. look up the utm zone of the locations of interest. I do this by first finding an approximate long/lat for my study area, then using that online to find the utm zone (e.g., http://www.apsalin.com/utm-zone-finder.aspx) 2. load the rgdal library (which loads the sp library) library(rgdal) 3. create a Spatial Points data object (1st argument is the x-y locations, 2nd argument specifies utms and the zone) locs - cbind(x,y) locs.sp - SpatialPoints(locs,CRS(+proj=utm +zone=your zone +north)) 4. transform to longlat trans - spTransform(locs.sp,CRS(+proj=longlat)) 5. now we can plot with maps library(maps) plot(trans,pch=1) map(county,add=T) Tammy On Thu, Jan 28, 2010 at 4:12 PM, danik danielle.k...@jcu.edu.au wrote: I'm just starting to use adehabitat to do home range calculations, and I'm wondering if there is a simple way to convert my xy coordinates (which are in decimal degrees) to UTMs or kilometers. The demo(homerange) already has their coordinates listed in kilometers, so I'm not quite sure how to get to that step. Another option would be to project my data. There is a package called mapproj, but I also am not sure how that works. I usually work with GIS so R is new to me. Any help is appreciated. Thank you. -- View this message in context: http://n2.nabble.com/adehabitat-data-projection-tp4476854p4476854.html Sent from the r-sig-ecology mailing list archive at Nabble.com. ___ R-sig-ecology mailing list R-sig-ecology@r-project.org https://stat.ethz.ch/mailman/listinfo/r-sig-ecology -- Tammy L. Wilson Doctoral Candidate Department of Wildland Resources Utah State University 5230 Old Main Hill Logan, UT 84322-5230 t...@aggiemail.usu.edu 435.797.3892 ___ R-sig-ecology mailing list R-sig-ecology@r-project.org https://stat.ethz.ch/mailman/listinfo/r-sig-ecology
Re: [R-sig-eco] scatter plot of coordinates
Hi Julia, I have found that the easiest way to display geographic data in R is to use a projected coordinate system (like Universal Transverse Mercator). You can then use plot (x,y) to display a scatterplot of your points. The resulting map isn't pretty, but it lets you visualize the data. The following packages have limited cartographic and map projection capabilities: maps, mapproj, maptools Also, the GIS program GRASS is free and quite functional. http://grass.osgeo.org/ Tammy On Wed, Jan 27, 2010 at 2:28 AM, Julia Tchernova tchern...@npolar.no wrote: Hello! I have a dataset with the date and positions - Lat and Long columns How do I make a scatter plot? Do I have to cbind the Lat and Long columns? Any suggestions will be much appreciated! Thank you Julia [[alternative HTML version deleted]] ___ R-sig-ecology mailing list R-sig-ecology@r-project.org https://stat.ethz.ch/mailman/listinfo/r-sig-ecology -- Tammy L. Wilson Doctoral Candidate Department of Wildland Resources Utah State University 5230 Old Main Hill Logan, UT 84322-5230 t...@aggiemail.usu.edu 435.797.3892 ___ R-sig-ecology mailing list R-sig-ecology@r-project.org https://stat.ethz.ch/mailman/listinfo/r-sig-ecology
