San Francisco Bay Area Regional Database (BARD)
Historical Map Imagery
The Western Region of the US Geological Survey has a large collection of archived historical topographic maps. The collection spans the entire history of USGS topographic mapping and is quite extensive for the state of California and the western region of the United States. In order to protect and preserve this irreplaceable collection of USGS topographic maps an electronic preservation program was commenced in 2002. The images on this website are a derivative of this program.
Original topographic maps in our archives were scanned as full size images (generally 18 x 22 inches). Images were scanned at 400 dpi in 24 bit RGB color in a .tiff file format. Filenames are a combination of the map name, the edition date, and the reprint date, if noted below the edition date.
For selected images, photo-processing has been completed to enhance the image. Processing was performed using Adobe Photoshop software and may include the following procedures;
Erasure of graffiti - extraneous hand written marks in the map margin have been removed.
Color correction - color values have been adjusted to remove the effects of aging of the paper.
Image Brightness - image contrast has been enhanced.
Images that have been adjusted have the letter "a" appended to the end of the file name.
Images are available in two file format;
- .jpg files: these have been created at a resolution of 200dpi with an image size of 8.5x11 for quick download and convenient printing on standard printers.
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.sid files: these files were originally created as .tiff files at a resolution of 400dpi and compressed utilizing MrSid image compression software from LizardTech, Inc. These images may be viewed using the ExpressView Browser Plug-in (MrSid) from Lizard, Tech. Inc.
![[expressview]](images/dl_expressview.jpg)
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