how to make buffer around shapefile in R

Question

I've read a similar post but couldn't apply the solution. Namely, I have a polygon of France's boundary and want to buffer it as follows:

fra_bound <- readOGR(dsn = "data/FRA_adm", layer = "FRA_adm0")
fra_buf <- gBuffer(fra_bound, width = 1000, quadsegs = 10)

The problem is this executes too long and throws: Error in gBuffer(fra_bound, width = 1000, quadsegs = 10) : std::bad_alloc

The projection of this shape is:

proj4string(fra_bound)

[1] "+proj=longlat +datum=WGS84 +no_defs +ellps=WGS84 +towgs84=0,0,0"

What am I doing wrong? Maybe I should use another way but I need it in R.

Answer 1

Your data is in Lat-long (EPSG:4326 by the look of it) so you are making a buffer of 1000 degrees which is going to wrap round the earth about three times!

You need to transform your spatial object to a different coordinate system based on metres (or km, or whatever units your 1000 is) using spTransform. I suspect for France there's a reasonable UTM zone with corresponding EPSG code. That will give you metres for a 1km zone with width=1000.

Note that for a whole country like France the outline may be very detailed and you might want to use gSimplify first to get a simpler outline.