Page:Geographic Areas Reference Manual (GARM).pdf/340

 land area only. (All bodies of water entirely or partially within a tabulation block are identified by a separate, untabulated block number—N99, where N= the block group number. As such, the water body is not part of the land block. This separate, untabulated block number exists internally within the TIGER data base, and also is included in TIGER/Line™ data products.)

In its TIGER data base, the Census Bureau has recorded the area of each polygon in square meters (1 square meter= 0.000001 square kilometer= 10.764 square feet= 0.000247 acre). The data base can accommodate a single polygon area measurement up to almost 2,150,000,000 square meters (2,150 square kilometers, or about 830 square miles). The area measurement for the land surface of any geographic entity is the sum of all polygons comprising that entity. The Census Bureau recorded the area measurement figures in the appropriate geographic reference files (but not in the TIGER data base) in thousandths of a square kilometer (0.001 square kilometer= 1,000 square meters= 10,764 square feet= 0.247 acre= 0.000386 square mile). These parameters ensured the reporting of precise area measurements in square miles and square kilometers, as well as any other appropriate measures—acres, square feet, hectares, and so forth. Where square mile figures are shown in the 1990 census data products, the conversion from square kilometers to square miles was performed first, and rounding was then applied—to six decimal places in the TIGER data base, to three in the summary tape files (STFs), and to one in the printed reports.

All water in the TIGER data base is classified in one of four types:
 * Inland water
 * Coastal water
 * Territorial sea
 * Great Lakes 15-6Area Measurement/Water Classification