The ZIP Code file in LandView® IV was prepared by the Bureau of Census from the U.S. Postal Service (USPS) City-State file (November, 1999). This file contains all 5-digit ZIP Codes defined as of November 1,1999 and the city, county and Post Office names associated with them. (Note: For ZIP Codes that cross county boundaries, the Post Office file assigns that ZIP Code to just one of the counties rather to each county.)
The Census Bureau then determined a geographic coordinate (latitude and longitude) for each ZIP Code in the City-State file by processing it against the Bureauís internal TIGER database for the state and county specified for the ZIP Code. (Before processing the file against TIGER, the Census Bureau excluded overseas military APO/FPO records from the file.) For those records where the ZIP Code could not be located in the TIGER database, the county internal point (in many cases the geographic centroid) was assigned to the ZIP Code. This typically occurred on records containing either a "P" or "U" in the ZIP_CLASS field.
The database structure, including field names, data types, field lengths, number of decimal places, and field descriptions for file ZIP_CODE.DBF are as follows:
ZIP_CODE C 5
The 5-digit zip code.
LATITUDE C 10
Latitude expressed as a signed integer with six decimal places. Negative numbers are in the southern hemisphere.
LONGITUDE C 11
Longitude expressed as a signed integer with six decimal places. Negative numbers are in the eastern hemisphere.
ZIP_CLASS C 1
Zip Code classification. Values are:
NAME C 28
USPS Post Office name.
STATE_CODE C 2
Federal Information Processing Standards (FIPS) state code.
COUNTY_CD C 3
Source: U.S. Census Bureau
Last Revised: Thursday, 26-Jan-2012 17:47:52 EST