No other image enhancements or manipulations were made. For the Web presentation, images were converted to LizardTech's MrSid format at a compression ratio of 40:1. Map image file sizes ranged from 600 MB to 1.3 GB each and were saved as uncompressed tiff files. Maps were scanned at 800 dpi, 24 bit color on an Anatech 4080C scanner. Maps were digitized at the USGS's National Mapping Division, initially at the Rocky Mountain Center, later at the Reston facility. Some editions of the quadrangles were published by the Corps of Engineers, the Army Map Service, or the Defense Mapping Agency. Efforts were made to only digitize first editions of quadrangles and not use reprint editions where the date of situation was uncertain. 350 maps were carefully selected to represent a historic perspective of the changing landscape of the region from rural to densely urban. Historic topographic maps are invaluable for tracking changes in land use, development of transportation systems, and growth of urban areas. Reyes south to Half Moon Bay and east to Antioch, Livermore and San Jose. These maps are in the Public Domain and have no copyright restrictions, and the geographic area selected is of high use and interest to our primary clientele, as well as off-site users.Īccess is provided to both the 15- and 7.5-minute USGS topographic quadrangles, spanning more than 100 years of mapping (1885-1999). Geological Survey's topographic quadrangles of the San Francisco Bay region were selected for digitizing. One-time funds were requested and received from the Library's collections budget to cover scanning and other project costs. This Pilot Project was first conceived in May 1999 to provide Web access to high use maps from the University of California-Berkeley's Earth Sciences and Map Library's collection.
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