----------------------------Original message---------------------------- We are pleased to announce the availability of Geocorr, Geographic Correspondence Engine. The MABLE / Geocorr geographic correspondence engine generates files and/or reports showing relationships between a wide variety of geographic coverages for the United States. This application allows you to specify the geographic scope of the correspondence files ( typically one or more complete states, but with the ability to specify counties, cities or metropolitan areas within states) and the geographic coverages to be correlated. Coverages available for correlation include all geographic units reported in the 1990 census Summary Tape Files, and several special "extension coverages", including congressional districts for the 103rd Congress and PUMAs used in the 1990 Pulic Use Microdata Samples (PUMS). Population, housing unit counts or land area can be used as the weighting variable to determine the proportion of correlation between units of the source geographic area codes and units of the target geographic area codes, or geocodes. MABLE - The Underlying Database MABLE is an acronym that stands for Master Area Block Level Equivalency file. This is the database that is used by the Geocorr engine to create correlation lists. "Block" here refers to 1990 census blocks, the smallest geographic units used in the 1990 census. It was chosen as the base unit for the application because the Bureau of the Census uses these blocks as the "atomic unit" for all other census based geographies. The MABLE database is a collection of 51 state-level datasets containing a total of nearly seven million block entries, each of which contains geographic code information to locate the block within all higher levels of the census geographic hierarchy. Geocorr- Building Correlation Lists Geocorr identifies the blocks that are within the scope of the area of analysis by units of source geocode and reaggregates them into the units of the target geocode. "Allocation" factors, the overlap or intersection between source and target geographies as determined by the chosen weighting factor, are calculated and reported. For example: County Tract Zip Population AFact 29510 1101.00 63109 1250 .500 29510 1101.00 63110 625 .250 29510 1101.00 63111 625 .250 This example shows that the scope of analysis is a single census tract, 1101.00, in a single county (the city of St. Louis, MO). The source geocode is the tract. The target geocode is the five-digit zip code. The sum of the population for each zip code within the tract equals the total population of the tract. The sum of the allocation factor (AFact) values is always 1.0. Access The Geocorr engine is available through the following two URLs: http://plue.sedac.ciesin.org/plue/geocorr http://oseda.missouri.edu/plue/geocorr The "sedac" site is the primary mirror, but both sites offer the same functionality at all times. This service is provided by the Socioeconomic Data and Applications Center (SEDAC). The Consortium for International Earth Science Information Network (CIESIN) has been designated by the National Aeronautics and Space Administration (NASA) to create and operate SEDAC, one of the data centers in the Earth Observing System Data and Information System (EOSDIS). SEDAC's mission is to develop and deliver information products and services that integrate social and natural science data in ways useful for decision making. For additional information about MABLE / Geocorr, SEDAC, or CIESIN, contact User Services at [log in to unmask] or call (517)797-2727 between 8 a.m. and 5 p.m. eastern time, Monday through Friday.