The zip code table must contain at least three columns, one each for the zip code, the longitude, and the latitude. Other columns in the table are not used. The default column names are zip, lon, and lat. Different column names may be used by calling the setZipColumn, setLonColumn, and setLatColumn methods. The name of the table defaults to zips but may also be changed using the setTableName method. The data needed for this class to operate properly can be obtained for free from several sources on the internet. One such source is the U.S. government census bureau. (http://www.census.gov/geo/www/gazetteer/places.html) This class was tested using the 1990 zip code file as the 2000 ZCTA file was not available when work started. The 2000 ZCTA file has a different format (represents longitude and latitude as +/-) which may have unexpected results. For help creating the database table see the documentation for your RDBMS.