Map Images Background Information
The Library's Web display of very large digital files is accomplished by using a wavelet compression technology made available to the Library of Congress by LizardTech. The multi-resolution seamless image database (MrSID) software used for the storage and retrieval of large digital images is a result of the research efforts at Los Alamos National Laboratory. In contrast to other compression software that relies on tiling, MrSID obtains its sharp resolution from a single compressed image, and it does not require any special hardware. MrSID allows immediate access to any part of an image, of any size, at any resolution.
The unique feature of MrSID is its ability to decompress only that portion of the image requested by the user. Compression ratio is approximately 22:1 depending on image content and color depth. MrSID is ideal for viewing maps, orthophotos, terrain models, and satellite data.
For additional information visit LizardTech's web site.
Scanning Cartographic Materials
Library of Congress
The digital images were created by staff in the Geography and Map Division by scanning the original map on a large-format (24 x 36 inches) flatbed scanner using a RGB (red-green-blue) 24-bit CCD color sensor (16.8 million colors). The scanner is manufactured by Tangent Image Systems. The Geography and Map Division has two Tangent scanners. One scanner is on indefinite loan from Tangent Imaging.
Each raster image is 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 transferred over a network to a Unix server for temporary offline storage.
Following scanning, the TIFF files are enhanced using the WindowsNT version of image processing software Adobe Photoshop 5.0, to rotate, crop, adjust brightness or contrast, and stitch together TIFF images for items requiring multiple scans.
The enhanced TIFF files are compressed, using a wavelet-based image compressing software called Multi-resolution Seamless Image Database, or MrSID. This software integrates multiple resolutions of an image into a single file which enables Internet users with a standard browser 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. LizardTech (http://www.lizardtech.com) of Seattle, Washington donated the license for the compression software.
The final step is the use of Alchemy Software to create a small GIF file for use as the initial thumbnail display of the item along with the bibliographic information.
After completing the scanning, an Archive TIFF file along with the SID and GIF files are stored on the Library's RS6000 World Wide Web server.
Specifications:
Master image:
Scanning resolution: 300 dpi
Tonal resolution: 24 bit color, RGB separation
File format: TIFF
Compression: none
Reference image:
Scanning resolution: 300 dpi
Tonal resolution: 24 bit color, RGB separation
File format: SID
Compression: Wavelet, 22:1 ratio.
Thumbnail image:
Viewing resolution: 72 dpi
Tonal resolution: 8 bit color, RGB separation
File format: GIF
Compression:none
Library of Virginia
The Library of Virginia’s Photo & Digital Imaging Services department scanned the maps using two types of scanners.
The first is a large-format (24 x 36 inches) flatbed scanner using an RGB (red-green-blue) 24-bit CCD (Charge Coupled Device) sensor (16.8 million colors). Tangent Image Systems manufactures this Artisan 2000 scanner (www.action-imaging.com). It can produce a 216 mega pixel image (12,000 x 18,000 pixels) which can produce a 618 MB file.
The second is a ZBE copy stand (www.zbe.com) with a Phase One Powerphase FX scanning back (www.phaseone.com). This scanning back uses and RGB 24-bit CCD sensor to produce 132 mega pixel images (10,500 x 12,600 pixels) up to 380 MB in size. The actual item can be up to 35 x 42 inches.
After scanning, each of the raw master image files is archived . Then a copy of the raw master file is made and and then opened in Adobe Photoshop (www.adobe.com) for cropping, color correction, contrast adjustment, sizing to 300 dpi (dots-per-inch) if necessary, and final naming. We do not stitch multi-part maps together. We use G4 Apple Macintosh computers (www.apple.com), using 1 GB of RAM, to run the Adobe Photoshop program and the Phase One scanning back’s acquisition software. The Tangent scanner uses proprietary software to acquire images and runs on a PC with 1 GB of RAM running Windows 2000. The Tangent files are then transferred over our network to our Apple Macintoshes for final image adjustment.
These images are then burned to CDs , one . A copy for storage and is stored for use here at the Library of Virginia; and one another copy is sent to the Library of Congress for MrSID image compression (www.lizardtech.com) and thumbnail display image for the web site. The CDS CDs are burned using the ISO 9660 standard, which allows cross platform compatibility with Unix, PCs, and Apple computers.
The raw master scans on CDs are stored offsite for safety.
Virginia Historical Society
Digital images of small manuscript maps were made by the staff of the Publications Department by scanning the original map on a Heidelberg Linoscan 1450 flatbed scanner using a RGB 24-bit CCD color sensor (16.8 million colors). Digital images of large maps were made by Archives staff by scanning the original map on a large-format (24 x 36 inches) flatbed scanner using a RGB 24-bit CCD color sensor (16.8 million colors). The scanner, manufactured by Tangent Image Systems, is located at the Library of Virginia. Digital images of oversized maps were created using a Phase One camera using a RGB 24-bit CCD color sensor (16.8 million colors) located at the Library of Virginia.
Images were saved at a resolution of approximately 300 dpi and converted into TIFF files. Following scanning, the TIFF files were enhanced using Adobe Photoshop v. 6.0 to rotate, crop, adjust brightness or contrast, and stitch together TIFF images for items requiring multiple scans. The images were then saved to CD-ROMs.
Compression (SID) and GIF files were created by the Library of Congress using the methods and software outlined above.
Master image: Please contact the Virginia Historical Society for these files
Scanning resolution: approximately 300 dpi
Tonal resolution: 24 bit color, RGB separation
File format: TIFF
Compression: none
Reference image:
Scanning resolution: 300 dpi
Tonal resolution: 24 bit color, RGB separation
File format: SID
Compression: Wavelet, 22:1 ratio
Thumbnail image:
Viewing resolution: 72 dpi
Tonal resolution: 8 bit color, RGB separation
File format: GIF
Compression: none
Cataloging the Geography and Map Division Collections
The majority of the Geography and Map Division's cataloging is full-level or complete, but the Division uses other levels of cataloging under certain circumstances. A number of years ago the Library instituted the use of minimal-level cataloging to increase the amount of material cataloged. These records can be easily recognized by the identifier MLC at the end of the call number, inserted before any filing location information.
In general, uncataloged items being added to American Memory receive an abbreviated, or adequate-level, cataloging record based on the information recorded on the folder created when the item was received and used for filing. These records can be easily recognized by the identifier TIL at the end of the call number, inserted before any filing location information.
The cataloging records for uncataloged items that have been described in a published bibliography are based on that descriptive information. These record are identified by the presence of the note Description derived from published bibliography.
The following comments, given in the order that the information is displayed, explain the general cataloging guidelines. They also point out some of the differences in the various levels of cataloging. For more information about cataloging cartographic materials, see Cataloging Tools.
TITLE. The title is transcribed from the original item. If the map carries no title one is devised from another sources or information and enclosed in square brackets. Devised titles are written by Library staff or they might come from a former owner.
The abbreviations "[sic]" and "[i.e.]" indicate erroneous spellings or information in transcribed titles. The correct information is provided as needed in the title or a note.
CREATOR. When the name of a person or a corporation that produced the item is known, only one form of the name is used, so that it is possible to retrieve all works by one creator under a single spelling or form of the name. Birth and death dates for persons are only included when such information is readily available and it is necessary to identify that person from another of the same name. If the Library of Congress form of the name was established while the creator was still alive, a death date is not usually added when the creator dies. It is expensive to update such information, and the name is already uniquely identified in the catalog.
The absence of a creator's name indicates that the creator is anonymous, unidentified, or unknown.
After the name, in a few instances, a term appears to identify the relationship(s) between the name and the work being cataloged, e.g. joint author.
CREATED/PUBLISHED. The publication information includes the place of publication, the publisher, date of publication, and, when appropriate, the place of printing, printer, and date of printing, enclosed in parentheses.
When this information is not readily available the cataloger supplies as much information as can be discerned from various clues shown as part of the publication or references sources. Information supplied from other sources are shown in square brackets.
When the single letter "c" appears before a date, it indicates the year in which the item was deposited for copyright.
NOTES. There are many types of notes. Notes provide clarification of the descriptive information or the content of the item, additional information about the item, or relationships with other works. The types of information that can be included in a note are sources of devised dates and titles, clarification of other topics shown, information about changes on this copy of the map such as a signature or other annotations, information on relief, etc.
A SUMMARY description may be included when the record was created from a published bibliography.