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indexing, and the ability, with a modest amount of hand sorting, 

 to group and regroup the data in any desired way. The information 

 from the data cards was used to develop the computer registry. 



A geographic inventory approach was developed so that each 

 element of data would be mapped at a common scale on a standard 

 base map of the entire Chesapeake Bay study area. Since there 

 was no existing map of the entire region sufficiently detailed 

 to portray area information such as wetlands or other important 

 natural areas, a base map was made using a mosaic of the seven 

 1:250,000 scale U. S. Geological Survey topographic maps of the 

 area. 



Data were mapped on transparent overlays to allow for 

 manipulation and analysis, and on topographic map base sheets 

 that could be inexpensively reproduced as osalid prints. Several 

 reproducible mylar base sheets were prepared, each containing a 

 photographic copy of the map mosaic and displaying the standard 

 information such as cities and towns, roads, topography, and 

 water features. 



Because of the need for more detailed mapping of specific 

 sites and natural phenomena, it was necessary to prepare a set 

 of 1:24,000 scale (7 1/2 minute) USGS topographic quadrangle maps 

 covering the study area represented on the 1:250,000 scale maps. 

 A complete set of 281 topographic maps was assembled and keyed to 

 the larger study area map by numerical index. 



