Geocoding

This is the one hard part about going open source geo.

Web services:

• Yonder - Compare geocoding results from multiple providers.
• GeoPy - Python library has a Yahoo and some opensource options.
• https://github.com/straup/js-geocoder
• https://github.com/straup/js-geolocation
• https://github.com/straup/js-reversegeocoder
• Edina Unlock - Excels with historic places but also uses modern UK data, and global modern places via GeoNames.org and Natural Earth.

Open source tools:

• pySHPgeocode - This Python package reverse geocodes data points to shapefile regions. It is developed primarily for assigning administrative region codes to a set of geo coordinates (in standard latitude/longitude). All you need is a shapefile of the regions you want to geocode to.
• OSM Nominatim - Used in OpenStreetMap, tied to OSM data.
• OSM Imposm.geocoder - Optimized for German addresses.
• MapQuest's version of Nominatim - Warning, assumes USA addresses.
• GeoCommons GeoCoder - an open-source Geocoder using open data mostly just for the US using Census geography files
• Gisgraphy - an open-source Geocoder using open data

###Not a batch geocoder, but useful:

• http://aaronland.info/iamhere/ - Decimal degrees, DDMMSS, geohash, and WOE ID place reverse geocode.
• Geonames Reverse Geocoder services list

###What's in a location?###

Location Types:

• Street Address: - An address consists of a street number, a street name, and a quadrant (NE, NW, SE, SW). The address number and street name are required.

Example: 441 4th ST NW

Results in a point XY, matches free text to points, polys, or street segment lines with addy ranges.

• Intersection: - An Intersection consists of two streets. Example: 14th ST NW and Pennsylvania Avenue NW, or 14th ST NW & Pennsylvania Avenue NW, or 16th ST NW over Military RD NW, or Military RD NW under 16th ST NW Results in a point XY, matches free text to points, polys.

• Block: - A block consists of a street and any other cross streets. Example: 4th ST NW from D Street NW to E Street NW or 400 Block of 4th St NW Results in a point XY or line segment, matches free text to points, polys, or street segment lines with addy ranges.

• Place, POI Names: - A place name consists of common place names (neighborhoods etc.) and public/institutional building names. Example: "White House" or "Dupont Circle" or "Wilson Building" or "Wilson High School" or "Woodrow Wilson House" Results in a point XY or polygon, matches free text to points, polys.

• Cities: - Both incorporated and unincorporated. Results in a point XY or polygon, matches free text to points, polys.

• Zipcodes: - Used for postal routing. Results in a point XY or polygon, matches free text to points, polys.

• States, counties, countries: - Other administrative units. Results in a point XY or polygon, matches free text to points, polys.

Image source: DC MAR