Getting Started with GEO, CouchDB, and Node.js

Chapter 2. Geographic Data

Geographic data comes in many formats. So many in fact, there could easily be a book based just on that subject, but to keep this simpler, here is an explanation of a few of the most common ones.

Shapefiles are one of the most common formats. The format was created and is maintained by ESRI, who also sells many tools for manipulating data in that format. The also sell other popular closed source GIS server and client software. The format is a mostly open specification for GIS data. Shapefiles spatially describe geometries, those can include points, polygons, and lines. A shapefile comes as a collection of files. At least 3 are required: .shp, .shx, and .dbf. Those files define shapes (the geometry), an index of the geometry features, and attributes for those features, respectively.

Shapefiles are widely available. Many government agencies use this format to publish public data. In fact, much of the data from free sources, public government data, or even data published by corporations will often times be in shapefiles. Learning to convert those shapefiles for usage in other formats is very useful.

Geo Datasets

There are many places that host public domained geographic data. Here is a small collection:

US Census (http://www.census.gov/geo/www/tiger/tgrshp2010/tgrshp2010.html)

The data is provided as shapefiles per state. This data is very complete and updated every 10 years. The last update was in 2010.

Natural Earth Data (http://www.naturalearthdata.com/)

This ...