LC National Digital Library Program announces release of Civil War Maps collection

[Tamara Swora-Gober <tswo@xxxxxxx>]

This message is being widely posted.

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The National Digital Library Program and the Geography and Map Division
announce the release of ?Civil War Maps? at:

http://memory.loc.gov/ammem/gmdhtml/cwmhtml

This collection documents battles, troop movements, reconnaissance
efforts and locations of fortifications and contains approximately 2240
Civil War maps and charts and 76 atlases and sketchbooks that are held
within the Librarys Geography and Map Division.  A selection of these
maps, based on the publication, ?Civil War Maps:  An Annotated List of
Maps and Atlases in the Library of Congress?compiled by Richard W.
Stephenson, will be made available through American Memory.  Updates
will be made to this collection on a monthly basis.

Though the large majority of these maps were created during the time of
the Civil War, a number were created afterwards to illustrate or explain
certain events or battles.  Publishers in the North and South created
maps included in this collection by both Union and Confederate forces. 
An introductory essay provides a discussion of mapping during the Civil
War highlighting materials that are within the Geography and Map
Division of the Library.

Of special interest are maps created by Major Jedediah Hotchkiss, a
topographical engineer for the Confederate Army. Hotchkiss?s
granddaughter donated these maps to the Library of Congress in 1948. 
Generals Lee and Jackson used a number of his maps as they planned
strategy for various battles.  Future updates will include images from
his notebooks, which contain detailed notes about his various map
projects.  Also included are maps that were owned by General William
Tecumseh Sherman.  Some of these maps, which were donated by members of
his family, document Sherman?s military campaigns in Tennessee,
Mississippi, Georgia and the Carolinas.  Users may also be interested in
maps that were created as propaganda items to encourage support of one
side or the other during wartime and maps that were published in various
newspapers.  Panoramic maps and city plans are included within the collection.

Digitizing the Collection
The digital images were created by staff in the Geography and Map
Division by scanning the original map on a large-format (24 x 34 inches)
flatbed scanner using RGB (red- green-blue) color separation.  Each
raster image was produced by scanning the item at a resolution of 300
dots-per-inch and converting the resulting proprietary file format to
TIFF format.  These TIFF files, which average approximately 180Mb, are
moved over a network to Surestore jukebox 1.3Gb magnetic optical
platters for temporary offline storage.

Following scanning, the TIFF files were enhanced using the WindowsNT
version of xRes, an image processing software, to rotate, crop, adjust
brightness or contrast, and stitch together TIFF images for items
requiring multiple scans.  The TIFF files were compressed, using a
wavelet-based image compressing software called Multi-Resolution
Seamless Image Database, or MrSID, from Lizard Tech.  This software
integrates multiple resolutions of an image in a single file which
enables Internet users to zoom in, getting more and more detail. 
Although MrSID is a "lossy" compressor, the images were compressed at a
ratio of 22:1 without experiencing any loss of information.  The final
step was the creation of a small GIF file for use as the initial
thumbnail display of the item.  After completing the scanning, the
Archive TIFF file along with the SID and GIF files are stored on the
Librarys RS6000 World Wide Web server. 

For questions please send email to maps@xxxxxxxx