Monthly Archives: May 2014

Projecting a map to match your data in R

I had a shapefile of lodgepole pine seed planning units (SPUs) in the BC Environment Standard Projection, which is an Albers Equal Area Conic projection with specific parameters. I tried creating a map with mapproject in R as explained by Kim Gilbert. I used an Albers projection with the parameters described here and in the .prj file associated with my data . But I couldn’t get the map of Western Canada and the shapefile of SPUs to plot together. I’m not sure why.

I took a different approach based on this StackExchange GIS question. I downloaded a shapefile for the world, projected it using rgdal::spTransform, clipped it to the extent I was interested in, and mapped it with the SPU shapefile. Map and code are below. Data for SPUs is not included.

map of lodgepole pine SPUs by Susannah Tysor

Map of Lodgepole Pine by Susannah Tysor in R with data from Tongli Wang


# Get basemap data
download.file(url="", "", "auto")

# read basemap shape file using rgdal library
ogrInfo(".", "ne_50m_admin_1_states_provinces_shp")
world <- readOGR(".", "ne_50m_admin_1_states_provinces_shp")

#project basemap to match spu shapefile
worldBCESP <- spTransform(world, CRS("+proj=aea +lat_1=50 +lat_2=58.5 +lat_0=45 +lon_0=-126 +x_0=1000000 +y_0=0 +ellps=GRS80 +datum=NAD83 +units=m +no_defs")) #proj4 string from

#make color palette for SPUS
palette(c("#8DD3C7", "#45B09E", "#2E766A", 
          "#FFFFB3", "#FFFF5C",
        "#BEBADA", "#BEBADA", 
        "#6860A9", "#9B95C6",
        "#80B1D3", "#498FC1", "#2A587A",
        "#FB8D0E", "#FDB462",
        "#83B828", "#B3DE69",
        "#F778BA", "#FCCDE5",
        "#ADADAD", "#D9D9D9",
        "#A053A2", "#5D315E", "#BC80BD", 
        "#94D585", "#54B63E", "#CCEBC5",
        "#FFEC5C", "#F5D800", "#FFED6F"))

# Read in shapefile for SPUs
spu <- readOGR("maps/SPUmaps/SPU_Tongli", layer="Pli_SPU")
levels(spu$SPU) <- c("Bulkley Valley-Central Plateau Transition High", "Bulkley Valley-Central Plateau Transition Low", "Bulkley Valley-Central Plateau Transition Mid", "Bulkley Valley High", "Bulkley Valley Low", "Bulkley Valley-Prince George Transition High", "Bulkley Valley-Prince George Transition Low", "Central Plateau High", "Central Plateau Low", "Central Plateau-Prince George Transition High", "Central Plateau-Prince George Transition Low", "Central Plateau-Prince George Transition Mid", "East Kootenay High", "East Kootenay Low", "Nelson High", "Nelson Low", "Nass Skeena High", "Nass Skeena Low", "Prince George High", "Prince George Low", "Prince George-Nelson Transition High", "Prince George-Nelson Transition Low", "Prince George-Nelson Transition Mid", "Thompson Okanagan High", "Thompson Okanagan Low", "Thompson Okanagan Mid", "Thompson Okanagan-Nelson Transition High", "Thompson Okanagan-Nelson Transition Low", "Thompson Okanagan-Nelson Transition Mid") #make levels human readable

#make plot
png("SPUmap.png", width=800, height=800)

plot(worldBCESP, xlim=c(0,1870556), ylim=c(157057.2,1421478), col="gray90") #plot basemap
plot(spu, add=TRUE, border=FALSE, col=spu$SPU) #plot SPUs
legend('bottomleft', legend = levels(spu$SPU), col = 1:length(levels(spu$SPU)), cex = 1, pch = 16) #plot legend
title("Lodgepole Pine Seed Planning Units")