# Follow Up on Spatial Overlays with R – Getting Altitude for a Set of Points

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A short follow up on a previous post on spatial overlays with R. **theBioBucket***, and kindly contributed to R-bloggers]. (You can report issue about the content on this page here)Want to share your content on R-bloggers? click here if you have a blog, or here if you don't.

library(sp) library(dismo) # some addresses in Austria pts <- geocode(c("Aldrans, Grubenweg", "Wien, Stephansdom", "Salzburg, Mozartplatz")) # make pts spatial coords <- SpatialPoints(pts[, c("longitude", "latitude")]) spdf_pts <- SpatialPointsDataFrame(coords, pts) # assign CRS/projection (which is WGS 1984) crs <- CRS(" +proj=longlat +datum=WGS84 +ellps=WGS84 +towgs84=0,0,0") proj4string(spdf_pts) <- crs # spatial data to extract (altitude) alt <- getData('alt', country = "AT") # convert alt from raster to grid (needed for over::sp) # and assign CRS (which is the same as spdf_pts, see > alt@crs) # don't mind warning - the CRS is the same.. spdf_alt <- as(alt, 'SpatialGridDataFrame') proj4string(spdf_alt) <- crs # view plot(alt) # plot pts on top plot(spdf_pts, cex = 2, col = 2, add = T) # check data str(spdf_pts) str(spdf_alt) # get the raster/pixel/grid data (> ?over): cbind(spdf_pts$interpretedPlace, over(spdf_pts, spdf_alt)) # result: # spdf_pts$interpretedPlace AUT_msk_alt # 1 Grubenweg, 6071 Aldrans, Austria 736 # 3 Saint Stephen's Vienna, Stephansplatz 1, 1010 Vienna, Austria 183 # 2 Mozartplatz, 5020 Salzburg, Austria 450

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