geocoding

geocoding

Intro, Options, and Workflows

What is Geocoding?

Turns a description of a location into geographic coordinates from spatial reference data.

Descriptor Examples

Input used to generate a lat/lng

• Zip Code
• Address
• Place Name
• Census Block

Spatial Reference Data Examples

Used to find and assign geographic coordinates

• Buildings
• Parcels
• Address Points
• Street Centerlines
• Zip Code Boundaries
• GNIS Place Names (USGS)

reverse geocoding

Coding of a point location (lat/lng) to a readable address or place name.

Familiar Examples

• Google Maps

Cascading Geocoder

Uses multiple geocoders and 'cascades' through them to find the best result.

Oregon's Geocoder

• Statewide Address Points
• Navteq Address Points
• ORTRANS - Street Centerlines
• GNIS Place Names
• Zip Code Tabulation Areas (Census)
• PLSS
• Oregon City Limits

Oregon's Geocoder Details

• http://navigator.state.or.us/arcgis/rest/services/Locators/gc_Composite
• Maintained by GEO
• Aggregate of authoritative and non-authoritative sources
• Returns information on which geocoder was used and score
• Public and free
• Limited to Oregon addresses

Other Available Geocoders

• Texas A&M
• Google Maps Geocoding API
• Yahoo
• ArcGIS Online - Esri World Geocoder
• Mapbox Geocoding API
• And Others...

Caveats of Using External Geocoders

• Usually limit to number of free geocodes
• License agreement can exclude storage of addresses
• Spatial reference dataset source abstracted out
• May not support batch geocoding

Recommendation

Let your project determine your geocoding solutions:

• Consider integrating multiple geocoding API's
• Take into consideration scalability
• Always take into account level of accuracy
• Make your results transparent

Using Oregon's Geocoder

• Input Address Fields
• Outuput Candidate Fields
• Properties
• API Reference / Help

Using Oregon's Geocoder

• REST HTTP Protocol
• HTML, JSON, KMZ Response

Example : Python

address = raw_input("Enter an address: ")

url = "http://navigator.state.or.us/arcgis/rest/services/Locators/" \
      "gc_Composite/GeocodeServer/findAddressCandidates?"
params = {'SingleLine' : address, \
          'outFields' : '*', 'f' : 'pjson'}

params_encode = urllib.urlencode(params)
url += params_encode

res = urllib.urlopen(url)
res_json = res.read()
res_dict = json.loads(res_json)
					

ArcGIS API's