R Classes and Methods for Spatial Data.

See:

• Pebesma, E.J., R.S. Bivand, 2005. Classes and methods for spatial data in R. R News 5 (2).
• Roger S. Bivand, Edzer Pebesma, Virgilio Gómez-Rubio, 2013. Applied Spatial Data Analysis with R, Second edition. Springer, NY.
• an sp maps gallery.