Lecture 6  georeferencing and geocoding
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Lecture 6 georeferencing and geocoding

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Lecture 6  georeferencing and geocoding Lecture 6 georeferencing and geocoding Presentation Transcript

  • Georeferencing and Geocoding Introduction to GIS – Spring 2013 1 M. Corbalis
  • Coordinate Systems vs. Georeferencing Systems• Coordinate systems define location• Georeferencing systems identify a location• The method of georeferencing must be: 1. Unique, linking information to exactly one location 2. Shared, so others can understand the meaning of a georeference 3. Persistent through time, so today’s georeferences still work tomorrow Introduction to GIS – Spring 2013 2 M. Corbalis
  • Georeferencing - TypesCoordinate Systems Some georeferences are metric; grid-based • They define location using measures of distance from fixed places. For example, distance from the Equator or from the Greenwich MeridianGeocoding Linear Referencing - based on ordering (ordinal) • Street addresses order houses along streets Gazetteers – based on place names (nominal) • Place names do not involve ordering or measuring Introduction to GIS – Spring 2013 3 M. Corbalis
  • Georeferencing - examplesLinear referencing and Gazetteers.• Similarity • taking natural language text and converting it into a coordinate in a known reference system – but are implemented differently.• Difference: • Linear referencing uses line features, often streets, as a base foundation • A gazetteer has a set of coordinates for all known place names. Introduction to GIS – Spring 2013 4 M. Corbalis
  • Uniqueness• Linear Referencing Systems and Gazetteers should both be comprehensive and unique.• A georeference may be unique only within a defined domain, not globally. Introduction to GIS – Spring 2013 5 M. Corbalis
  • Uniqueness • London England, UK• London Ontario, CA • London Alabama - Conecuh County• London Belize • London Alabama- Montgomery County• London Equatorial Guinea • London Arizona• London Finland • London Arkansas• London Kiribati • London California• London Nigeria • London Indiana• London South Africa - Limpopo • London Kentucky• London South Africa - Noordprovincie • London Michigan• London South Africa - Graskop • London Minnesota • London Missouri • London Ohio • London Richland County • London Oregon • London Pennsylvania • London Tennessee • London Texas • London West Virginia • London Wisconsin Introduction to GIS – Spring 2013 6 M. Corbalis
  • GeocodingAddress Locators• The address locator is the main tool for geocoding in ArcGIS.• It is a dataset that contains information including address attributes, indexes, and queries for geocoding.• An address locator contains a snapshot of the reference data that is used for geocoding.• In the process of geocoding, the reference data is no longer needed after the locator is created.ESRI Definition: A dataset in ArcGIS that stores the address attributes, associated indexes, and rulesthat define the process for translating non-spatial descriptions of places, such as street addresses, intospatial data that can be displayed as features on a map. An address locator contains a snapshot of thereference data used for geocoding, and parameters for standardizing addresses, searching for matchlocations, and creating output. Address locator files have a .loc file extension. Source: ESRI Introduction to GIS – Spring 2013 7 M. Corbalis
  • GeocodingAddress Locators – Linear Referencing (U.S. Census Bureau TIGER/Line Shapefiles) Source: U.S. Census Bureau Introduction to GIS – Spring 2013 8 M. Corbalis
  • GeocodingAddress Locators – Linear Referencing (U.S. Census Bureau TIGER/Line Shapefiles) • The TIGER method, using vector features to represent roadways and address range attributes to enable address geocoding, is a common features of proprietary geographic databases. • Used by GPS for directions • Used in business and government for marketing, trade area analysis, districting, routing, and allocation etc. Source: U.S. Census Bureau Introduction to GIS – Spring 2013 9 M. Corbalis
  • ESRI Locators• ESRI_Places_World Use the World Places Locator to geocode world places: countries, states and provinces, administrative areas, cities, landmarks, water bodies, and more.• TA_Address_EU Use the European Address Locator to geocode addresses in Europe including street address, street name, city,• TA_Address_NA_10 (Use this ArcGIS 10 style North American Address Locator) Use this to geocode addresses in the United States and Canada: street address, ZIP/postal code, city/state or city/province, and more. This locator supports a single line input field and output in different spatial reference.• TA_Streets_US_10 (ArcGIS 10 style United States Street Locator) Use this to geocode street addresses in the United States. This locator supports a single line input field and output in a different spatial reference. You can also create a new address locator based on the data you have. Introduction to GIS – Spring 2013 10 M. Corbalis
  • Online Locators - FreeName Free Limit API Reference DataUSC WebGIS Geocoder Unlimited yes SeveralGeocoder.us 50,000/day yes TIGERYahoo 5,000/day yes NavteqGoogle 15,000/day yes TeleAtlasAjm Software 10/day yes TIGERFFIEC 1 at a time no TeleAtlasGeonames.org 20,000/hr yes Unknowndiddlefingermaps.huge.info unlimited but one at a time nomultimap 1% of the communitys total traffic yes possibly microsoft maps.live.comNearby.org.uk 50-100 requests an hour US, UK PostcodesViaMichelin.co.uk 1000 per dayterraserver unlimited yesbromit.com unlimited noTravel GIS 1 free no NAC Geographic Products Source: USC Spatial Sciences Institute Introduction to GIS – Spring 2013 11 M. Corbalis
  • Online Locators - PayName Free Limit/Cost API Reference DataTeleAtlas EZ-Locate 100 free, 25,000 for $410 - 100,000 for $1,535 yes TeleAtlas Microsoft MapPoint WebNAC Geographic Products 1,000 addresses for 39 euros yes ServiceThinkGeo no One-time Setup fee: $2,500.00, monthly minimum:Spatial Insights $200.00 for 15,000 noiBegin 100 free, $.01/geocode after that yesProxix $18.00 per 1000 yes parcel level, navteqTerraPages yes G-NAF• Google Source: USC Spatial Sciences Institute Introduction to GIS – Spring 2013 12 M. Corbalis
  • Geocoding MethodsRooftop / Parcel• Usually the most precise (and most expensive) geocoding methodology.• There are 144.3 million privately owned parcels in the US.• As digital parcel boundaries become available they are rapidly being incorporated into public access or third party vendor databases.• A geocoding application that uses parcel data will typically associate the coordinates of parcel center (‘centroid’) of the parcel (property). Source: Teradata, Inc. Introduction to GIS – Spring 2013 13 M. Corbalis
  • Geocoding MethodsRooftop / Parcel Geocoding Source: Teradata, Inc. Introduction to GIS – Spring 2013 14 M. Corbalis
  • Geocoding MethodsStreet Interpolation• Uses street data where the street network is already coded within the geographic coordinate space (e.g. TIGER, Navteq, MapInfo etc. )• Each street segment is associated with an address range• Software takes an address, matches it to a street and a specific segment, then interpolates the position of the address within the segment• Errors ranging from 50 feet up to several thousand feet are not uncommon,• Interpolated Geocodes should not be used in applications that require extremely high accuracy Source: Teradata, Inc. Introduction to GIS – Spring 2013 15 M. Corbalis
  • Geocoding MethodsStreet Interpolation Source: Teradata, Inc. Introduction to GIS – Spring 2013 16 M. Corbalis
  • Geocoding MethodsCentroid Interpolation Geocoding• It is using the center (‘centroid’) of the area the object is in, instead of the road network as the street level interpolation.• It ranges from the precise (rooftop interpolation in the case of parcels) to the very approximate (e.g. Census Blocks or Zip Codes) Source: Teradata, Inc. Introduction to GIS – Spring 2013 17 M. Corbalis
  • Geocoding MethodsCentroid Interpolation Geocoding Source: Teradata, Inc. Introduction to GIS – Spring 2013 18 M. Corbalis
  • Geocoding MethodsOther Linear Referencing Systems• Based on distance and direction along a linear network• Transportation agencies often measure locations of features or events along transportation network links (e.g. a traffic accident occurred at the 52.3 milepost on a specific highway). Source: Teradata, Inc. Introduction to GIS – Spring 2013 19 M. Corbalis