15 Geocoding addresses IN THIS CHAPTER Managing geocoding services in ArcMap Controlling the geocoding process Finding an address Geocoding a table of addresses Rematching a geocoded feature class A feature is an object that has geometry In most cases this geometry is captured by digitizing or scanning paper maps In many cases however geographic data exists that indirectly captures geometry by describing locations such as street addresses city names or even telephone numbers While humans understand what these descriptions mean and how they relate to locations on the earth s surface computers do not In order to display these locations on a map and perform analyses with them a computer must be given geometric representations such as point features of these locations Geocoding also commonly known as address matching is the process of creating geometric representations for descriptions of locations A geocoding service defines a process for converting alphanumeric descriptions of locations into geometric shapes You can use geocoding services in ArcMap to find individual addresses and to geocode tables of addresses You can also review and rematch the feature classes and shapefiles that you create by geocoding tables of addresses In order to geocode in ArcMap you must first define geocoding services For information on creating geocoding services see Using ArcCatalog 411 Ch15 p65 12 06 2000 1 30 PM 411 Adding a geocoding service to an ArcMap document Managing geocoding services in ArcMap In ArcMap you can find addresses or geocode tables of addresses using geocoding services Your ArcMap document can contain any number of geocoding services You can use the Geocoding Services Manager to manage the set of geocoding services contained in an ArcMap document 1 Click the Tools menu point to Geocoding then click Geocoding Services Manager 2 Click Add 1 3 Browse for the geocoding service that you want to add to the ArcMap document and click Add 4 Click Close 2 For information on creating geocoding services see Using ArcCatalog 4 3 412 Ch15 p65 USING ARCMAP 412 12 06 2000 1 30 PM Removing a geocoding service from an ArcMap document 1 Click the Tools menu point to Geocoding then click Geocoding Services Manager 2 Click the geocoding service that you want to remove from the ArcMap document then click Remove 1 3 Click Close 2 3 GEOCODING ADDRESSES Ch15 p65 413 413 12 06 2000 1 31 PM Controlling the geocoding process The geocoding process Once you have added a geocoding service to an ArcMap document you can begin geocoding addresses with it However understanding how a geocoding service matches addresses and how modifying a geocoding service s settings affects this process can help you improve both the performance and accuracy of your geocoding Geocoding services use a specific set of steps to find a match for an address First the geocoding service standardizes the address Second the geocoding service searches the geocoding reference data to find potential candidates Next each potential candidate is assigned a score based on how closely it matches the address Finally the address is matched to the candidate with the best score When a geocoding service standardizes an address it dissects the address into its address components For example the address 4 Dundas St E has four address components the street number 4 the street name Dundas the street type St and the street direction E Each style of geocoding service standardizes an address into a different set of address components Street type Street number 4 DUNDAS ST E Street direction Street name A geocoding service standardizes an address into a number of address components If your geocoding service uses a place name alias table it searches this table for entries that match the address you are trying to geocode to determine if the address is actually a place name alias If one is found it substitutes the address in the place name alias table for the place name that you are trying to locate and standardizes this address Once it has standardized the address the geocoding service searches the reference data to find features with address components that are similar to the components of the standardized address Each style of geocoding service bases this search on a different set of address components The geocoding service uses its spelling sensitivity setting for some address components such as street name to determine how closely the address components of a feature must match the address components of the address you are geocoding If the geocoding service uses an alternate street name table then it also searches this table to find potential candidates The geocoding service searches the reference data for features with address components that are similar to the components of the standardized address Once the geocoding service has generated a set of potential candidates it scores each potential candidate in order to determine how closely each potential candidate matches the address that you are geocoding Each potential candidate is assigned a score from 0 to 100 Each address component is used to generate this score The score for each potential candidate will be lower if address components are misspelled for example the street name is misspelled incorrect for example the street number of the address does not fall within the address range for the candidate or missing for example the street direction is specified in the 414 Ch15 p65 USING ARCMAP 414 12 06 2000 1 31 PM address but not in the potential candidate Once each potential candidate is scored the geocoding service generates a set of match candidates The geocoding service determines which potential candidates are match candidates using its minimum candidate score setting The geocoding service scores each potential candidate using all of the address components A set of match candidates is generated based on the geocoding service s minimum candidate score setting Finally the geocoding service finds the match candidates with the highest match score If the score of the match candidate with the best match score exceeds the geocoding service s minimum match score setting then the geocoding service matches the address to that match candidate Geocoding service settings Geocoding services have a number of settings that allow you to control the geocoding process These settings control how a geocoding service reads a table of addresses that you want to geocode how it matches addresses to features in the reference data