tmp | R Documentation |
A raster dataset showing Canadian Arctic between Longitude -140 to -50 and latitude 65 to 80. The raster are in Sinusoidal Eaqual area projection with grid resolution of 9.28km. The landmass are masked by GSHHG (http://www.soest.hawaii.edu/pwessel/gshhg/index.html) costaline data.
A rasterLayer object
Chih-Lin Wei <chihlinwei@gmail.com>
# Example on making a raster template of the Canadian Arctic library(raster) library(maptools) #### Create a global empty raster #### # 9km or 1/12 degree global grids tmp <- raster(nrow=2160, ncol=4320, xmn=-180, xmx=180, ymn=-90, ymx=90) tmp <- setValues(tmp, numeric(2160*4320)) #### Subset the raster to Canadian High Arctic #### ex <- extent(c(-140,-50,65,80)) tmp <- crop(tmp, ex) plot(tmp) #### Download GSHHG costaline data #### # Create a folder in the parent directory to save GSHHG data dir.create("../Arctic_ocean_data") # GSHHG FTP server address and path to save zip file url <- "ftp://ftp.soest.hawaii.edu/gshhg/gshhg-bin-2.2.4.zip" dest <- "../Arctic_ocean_data/gshhg-bin-2.2.4.zip" # download will take a while (109.2 Mb) download.file(url, dest, mode="wb") # Unzip the data; use gshhs_h or gshhs_f if higher resolution is needed unzip(dest, files = c("gshhs_i.b", "gshhs_l.b", "gshhs_c.b"), exdir = "../Arctic_ocean_data") file.remove(dest) # Remove zip file; omit if you want keep it #### Mask landmass using GSHHG costaline polygons #### # Read GSHHG data # getRgshhsMap() take longitude limits within 0-360 land<-getRgshhsMap("../Arctic_ocean_data/gshhs_l.b", xlim=c(360-140, 360-50), ylim=c(65, 80), level = 1, no.clip = TRUE) plot(land, xlim=c(-140, -50), ylim=c(65, 80)) # Mask the raster by landmass tmp <- mask(tmp, land, inverse = TRUE) plot(tmp) # re-project the raster template to Sinusoidal Equal Area Projection sinu <- "+proj=sinu +lon_0=-95 +x_0=0 +y_0=0" tmp <- projectRaster(tmp, res = 9280, crs = sinu) # Grid resolution is 9.28 km plot(tmp) # Export the raster template names(tmp) <- "template" writeRaster(tmp, "../Arctic_ocean_data/template.grd", format = "raster", overwrite=TRUE)
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