Geocoding: - Table to geocode may be an ASCII, spreadsheet, dBase, or MapInfo table - Referred to as the “target” table - The target table is the attribute table that we want to spatially locate on a map

Geocoding: - Table that will be used to reference or match the attribute data - Referred to as the Reference Database or the “Search Table” - In this example, the search table is the TIGER centerline file

2 methods of Geocoding: 1. Address (Interpolation method)- places point along street centerline Target 1225 Main St. Reference (Search db) Main St Polygon- places point at centroid (weighted center) of polygon Target Reference OR 1225 Main St Zip code Parcels Main St Main St

Address (Interpolation) Method

Steps to Geocode:

Classes of match results: Incorrect Match: Data record matched to incorrect segment. The house address value in the target db is written wrong. ie Main St. typed wrong – really should be 100 Main St. Nonmatch that could be matched. A portion of the address in the target db is written wrong. ie. Main Ave. in target db but should be Main St. Correct match: Obviously, this is what we want!!!! Correct Nonmatch (unmatchable record): No match can occur ie. A new road is made, but the information about the road has not been added to the reference data

The following slides step through the geocoding process using the address method (interpolation) in MapInfo 1. Open the target db (table to geocode) 2. Determine field to use to geocode 3. Run the table of addresses through an address standarizer (if available) 4. Determine if a field such as such as zip code or city exists so that you use the refine search option with a polygon file 5. Create a new field to store the geocode result code (code gives idea why matches did not occur)

Determine the reference db to use. Determine the key field that will be used as the match in the reference table. Determine the field name of the polygon file that contains the zip or city Reference db- Street Centerline

In MapInfo, Select Table> Geocode leaks Address Street_centerline Street Zip Zips_Ohio Zipcode A B 1 = the table used to find a x,y spatial location 2 = the field to use to locate & attempt to match to #4 3 = the reference data layer that already has a spatial location 4 = the field in the reference table that is used to locate the value in field #2 of the table to geocode 5 = a secondary reference data layer (i.e. zip or city) that allows for more accurate geocoding results- (101 Main St in Berea or 101 Main St in Parma) 6A = field value used to match to #6B of the geocode table 6A MUST be filled in prior to 6B

Geocoded points result using address matching to street centerline Interpolation Method

Result code values Any negative value means that the record did not geocode The code may give you an idea of the error.

Geocoding using the polygon method

Geocoding using both Interpolation and Polygon Methods Comparison Polygon Method Interpolation Method