I've also discovered the bathymetry / topography data from GEBCO. Again, very easy to import into R from the netCDF files.
The above map of the Galapagos Archipelago illustrates the quality of both datasets. It also shows the comparison of coastline accuracy between World Vector Shoreline (1:250,000), world (map package), and worldHires (mapdata package) datasets. Obviously, the low-resolution world data only makes sense for quick plotting at large scales, but the high-resolution data is as much as 1/10° off in some locations. I noticed these errors for the first time when trying to map some data for smaller coastal bays. It drove me crazy trying to figure out where the errors were - in my data locations or the map itself. Bathymetry used in the map was 30 arc-second resolution GEBCO data.
[EDIT: The comparison of coastline data now includes the high resolution data from the rworldmap package.]
A more detailed description export settings:
- Coastline data (from 'Coastline Extractor') :
- Coastline database: World Vector Shoreline (1:250,000)
- Compression method for extracted ASCII data: None
- Coast Format options: Matlab
- Coast Preview options: GMT Plot
- Bathymetry / topography data [link]:
- General Bathymetric Chart of the Oceans (GEBCO) : GEBCO_08 Grid (30 arc-second resolution)
For both maps, I took inspiration for the color palettes from GMT. The rgb color levels of these palettes have got to be documented somwhere, but I gave up looking after a while and managed to hack their levels from color scales contained in .png files [link].
Below is the R code to reproduce the figures.