Overview: What is Geocoding

Geocoding:  A practical definition 
The process of making data records "mappable". 

Before geocoding:

After geocoding:

Geocoding:  A technical definition

• The process of matching records in two databases: your address database (without map position information) and a reference street map or other "address dictionary".

• Geocoding software (e.g., MapInfo Pro or MapMarker) links records in the two databases by matching street names and address numbers.

• When your database records are successfully matched to a reference street map database, your records are tagged with the correct map positions, typically lat-lon coordinates.

• Thereafter, your data table carries its own position information and can be mapped without the reference street map or address dictionary.

• MapInfo Pro, by default, hides the map coordinates:  i.e., it does not list the Lat-Lon values in the tables. But it uses the coordinates, nevertheless, behind the scenes.

Before geocoding:

After geocoding:

Why geocode with street address precision?

To see location patterns more clearly

You can map addresses by zip code, of course, without geocoding at the street level. This produces a very coarse picture compared to a address-level point map.

	After geocoding by zip code		After geocoding by address

To summarize data by any region

• Which district office should handle the new client?  Geocode client addresses by street address and see which territory region they fall within.

• Are capital improvement projects benefiting all legislative districts equally? Find out by geocoding the street addresses of the capital projects then overlaying the legislative districts. 

• Banks and insurance companies often report statistics by census tract. To determine the census tract for a loan or depositor, geocode the street addresses, overlay the tract map, then use Query > SQL Select to summarize by tract.

To target more precisely

• We may make assumptions about households  based on the characteristics of the neighborhoods where they live.  If geocoded by street address, we can associate household records with smaller, more homogenous areas such as block groups.  This results in more accuracy. 

• As shown below, the demographics of block group areas can be dramatically different than the demographics of zip codes.

	Higher income zip codes		Higher income block groups

Geocoding: Part of modern corporate customer information systems

More and more Fortune 1000 corporations are geocoding all their customer addresses as a standard practice.  By making map position part of their overall corporate information system design, all areas of the organization can take advantage of spatial analysis techniques.

MapInfo Pro:  The original street-level geocoder

The original way to geocode used MapInfo's built-in geocoding engine along with a street map.  MapInfo Corp pioneered this technique for PCs, releasing MapInfo (for DOS) in 1987.   MapInfo for Windows, released in 1992, also offered street level geocoding using displayable and user-editable street maps.

• Geocoding is accessible via the MapInfo menu option   Table  > Geocode ...   Just add street map data.

• Requires a street map with street names & address ranges: e.g., "StreetPro", "StreetInfo" or comparable.

• Uses an "abbreviation file" (e.g., mapinfow.abb) to standardize some address components: e.g., "Street", "Str", and "St".

• Can use a City or Zip code boundary map to distinguish addresses that occur in more than one place in a county.

Advantages of MapInfo Pro

• Can be cheaper than MapMarker, if all addresses are in a single or few counties, especially if local government street data is available.

• Street address information in street tables is completely editable. Missing a street?  Just draw it and fill in the street name and address fields.  You can match against this new street immediately..

• Can easily use new street map information generated by local governments.

• Suitable for use in Mexico & other countries for which MapMarker versions may not (quite yet) be available.

• Can be used for reverse-geocoding (EAL version only):  ie., look up nearest address based on lat-lon.

MapMarker:  Single-purpose stand-alone geocoder

MapMarker is a standalone geocoder software program, introduced by MapInfo Corp. in 1996 and now at Revision 8.3.   It can run independent of MapInfo Pro and is optimized to do one thing:  geocode quickly. 

It is a combined software and data product: i.e., it comes with its own street address reference data files (aka "address dictionary"), and regular data updates.

It is available in three versions, each with different pricing and different levels of precision:  MapMarker Zip4, MapMarker, & MapMarker Plus.

• Consider placing and selecting points at the edge of the area to be partitioned.

Advantages of MapMarker

• Cheaper, except for single-county applications.

• One-step geocoding, even if addresses are in many different counties across the US.

• Cleans or standardizes addresses, zip codes, zip+4 codes on the fly.  Can produce USPS "CASS-certified" mailing lists.     [CASS-certified means lower postage rates for bulk mailers.]

• Includes Zip+4 reference files and can automatically compute the Zip+4 code and geocode to the Zip+4 location as a fallback, if it cannot match to exact street address.

• Very fast: SGSI has processed 1,000,000 records in under 2 hours.

• Adds census tract, block group, and block codes to the address record as part of its single-pass processing.  No separate SQL processing required.

• Friendly, straightforward user-interface. Easy to use.

• Is engineered as a true client-server application and can be used as the geocoding engine for a web server, for example.

• More sophisticated "rule based" matching algorithms are better than those in MapInfo.  Offers a better set of "close-match" candidates than MapInfo.

• Can geocode address lists stored in a remote server database (Oracle, Informix, etc)

• Address and street data is not directly user-editable.  However, power users can build & compile their own custom MapMarker-format databases and use them to supplement MapMarker's standard databases.

• Can process sets of address files, running in "batch" mode.

Note:  Except for the "County" option, StreetPro, Zip code, and MapMarker Plus costs are ballpark annual costs for a one-user desktop license, payable at the beginning of each year and assume a 3-year subscription.  Web server usage costs more.  The cost of MapInfo Pro is not included.

MapInfo Pro:

"Chapter 8: Geocoding"
MapInfo 7.0 User Guide, pp. 138ff.

"Appendix B:  Advanced Geocoding" pp. 577ff
MapInfo Pro 7.0 User Guide

MapMarker Plus

MapMarker User Manual, 400 pp.  plus short "Getting Started".

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