tmp: A raster template of the Canadian Arctic

In chihlinwei/OceanData: Tools to download and extract oceanographic data from various sources

A raster template of the Canadian Arctic

Description

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.

Format

A rasterLayer object

Author(s)

Chih-Lin Wei <[e-mail]>

Examples

# 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)

chihlinwei/OceanData documentation built on Sept. 26, 2022, 2:47 p.m.