Time for action – adding shapefiles

You'll notice a lot of results from doing a Google search for shapefiles. This is the most common format to exchange GIS data sets. Let's download one of those and publish it as a layer.

1. Download Tiger 2011 county census data as a shapefile and place it in an appropriate folder:

   ~/shapes$ wget http://www2.census.gov/geo/tiger/TIGER2011/COUNTY/tl_2011_us_county.zip

2. Unzip the archive:

   ~/shapes$ unzip tl_2011_us_county.zip
   Archive:  tl_2011_us_county.zip
     inflating: tl_2011_us_county.dbf
     inflating: tl_2011_us_county.prj
     inflating: tl_2011_us_county.shp
     inflating: tl_2011_us_county.shp.xml
     inflating: tl_2011_us_county.shx

   Note

   In fact a shapefile is not a single file. According to specifications (http://www.esri.com/library/whitepapers/pdfs/shapefile.pdf), you need at least three files with shp, dbf, and shx extensions. Although not strictly required, it is really worthwhile to also have the .prj file. It contains the SRS definition for the data contained...