On 13/01/2017 10:59, Miluji Sb wrote: > Thank you for your reply. This is what I did: > > ### > library(data.table) > library(raster) > library(rgdal) > library(foreign) > > elevation_world <- getData('worldclim', var='alt', res=2.5) > > # Aggregate Elevation to 1 degree > elevation_world_1deg <- aggregate(elevation_world, fact = 24, fun = sum)
Aggregating with fun=sum is a bit strange for elevation. mean or median would certainly be a better choice. > > # Extract by lon lat (1° x 1° - gcp_grid) > elevation <- cbind(gcp_grid, alt = extract(elevation_world_1deg, gcp_grid)) gcp_grid are points or polygons? If they are polygons, there's no need for the aggregation step above. Also have a look at df = TRUE, which returns a dataframe, and sp=TRUE, which returns a Spatial*DataFrame with extracted values cbinded to the attributes of the original Spatial*DataFrame. (both are arguments of raster::extract) Cheers, Loïc > > elevation <- as.data.frame(elevation) > ### > > Is this correct? Thanks again! > > Sincerely, > > Milu > > On Fri, Jan 13, 2017 at 3:11 AM, Bacou, Melanie <m...@mbacou.com> wrote: > >> R raster::getData("SRTM", ...) will return elevation rasters at 90m >> resolution. >> See: >> https://www.rdocumentation.org/packages/raster/versions/2.5- >> 8/topics/getData >> http://www.cgiar-csi.org/data/srtm-90m-digital-elevation-database-v4-1 >> >> --Mel. >> >> >> On 1/11/2017 6:26 AM, Miluji Sb wrote: >> >>> Dear Michael, >>> >>> Thank you for your reply and the suggestions. >>> >>> Ideally, I would like a raster from which I can extract elevation at 1° x >>> 1° resolution. I do not have much experience with working with DEM but >>> have >>> work with data such as GPW. >>> >>> I will definitely look at the datasets. Could you kindly suggest one that >>> I >>> could convert to raster and extract? Hope that's not a silly question. >>> >>> Sincerely, >>> >>> Milu >>> >>> On Wed, Jan 11, 2017 at 1:51 AM, Michael Sumner <mdsum...@gmail.com> >>> wrote: >>> >>> Passed through? Maybe you want ?raster::extract >>>> >>>> There are a few versions of global elevation on CRAN, necessarily at low >>>> resolution but no overall summary afaik (someone should do this :). >>>> >>>> This is one: https://cloud.r-project.org/web/packages/GEOmap/index.html >>>> >>>> If you have the stomach for development versions of packages see elevatr: >>>> https://github.com/jhollist/elevatr >>>> >>>> I tend to have the high-resolution files at hand because we use them >>>> constantly, the main ones are Gebco14/Gebco08 and Etopo1/Etopo2 (from >>>> Smith-Sandwell). >>>> >>>> There's a reasonable overview here, you probably should find a specific >>>> data set that is at the resolution you are after already, and you can >>>> cite >>>> its derivation for your work: >>>> >>>> http://vterrain.org/Elevation/global.html >>>> >>>> Cheers, Mike. >>>> >>>> On Wed, 11 Jan 2017 at 10:20 Miluji Sb <miluj...@gmail.com> wrote: >>>> >>>> Dear all. >>>>> >>>>> Is there a way to download global elevation data at the 1° x 1° >>>>> resolution >>>>> in R using a given set of coordinates? >>>>> >>>>> I know about the getData() function but can many coordinates be passed >>>>> through this? Thanks! >>>>> >>>>> Sincerely, >>>>> >>>>> Milu >>>>> >>>>> [[alternative HTML version deleted]] >>>>> >>>>> _______________________________________________ >>>>> R-sig-Geo mailing list >>>>> R-sig-Geo@r-project.org >>>>> https://stat.ethz.ch/mailman/listinfo/r-sig-geo >>>>> >>>>> >>>>> University of Tasmania Electronic Communications Policy (December, >>>>> 2014). >>>>> This email is confidential, and is for the intended recipient only. >>>>> Access, disclosure, copying, distribution, or reliance on any of it by >>>>> anyone outside the intended recipient organisation is prohibited and >>>>> may be >>>>> a criminal offence. Please delete if obtained in error and email >>>>> confirmation to the sender. The views expressed in this email are not >>>>> necessarily the views of the University of Tasmania, unless clearly >>>>> intended otherwise. >>>>> . >>>>> >>>>> -- >>>> Dr. Michael Sumner >>>> Software and Database Engineer >>>> Australian Antarctic Division >>>> 203 Channel Highway >>>> Kingston Tasmania 7050 Australia >>>> >>>> >>>> [[alternative HTML version deleted]] >>> >>> _______________________________________________ >>> R-sig-Geo mailing list >>> R-sig-Geo@r-project.org >>> https://stat.ethz.ch/mailman/listinfo/r-sig-geo >>> >> >> > > [[alternative HTML version deleted]] > > _______________________________________________ > R-sig-Geo mailing list > R-sig-Geo@r-project.org > https://stat.ethz.ch/mailman/listinfo/r-sig-geo > _______________________________________________ R-sig-Geo mailing list R-sig-Geo@r-project.org https://stat.ethz.ch/mailman/listinfo/r-sig-geo