Methods to calculate U.S.A. zip code distances and city proximities. Returns the distance in miles between two zipcodes. Returns a set of locations within the radius of the given zipcode. Returns a set of zipcodes for the SOUNDEX of the given city. Returns the distance in miles between two zipcodes. Returns a set of locations within the radius of the given zipcode. Returns a set of zipcodes for the SOUNDEX of the given city. Returns the distance in miles between two zipcodes. Returns a set of locations within the radius of the given zipcode. Returns a set of zipcodes for the SOUNDEX of the given city. Methods to calculate U.S.A. zip code distances and city proximities.