Maps are scanned by institutions from across the PALMM consortium, by large- and small-scale digitization programs alike, and a variety of imaging technologies is employed. Imaging technologies, for the most part, are fully digital, relying upon digital camera backs. Some oversized maps are digitized from analog 105 mm color-film format intermediaries, while others - as a consequence of the artifacts history has bequeathed to us - have been digitized from 35 mm color-slide film. Some small maps are digitized with the aid of flatbed scanners. The technical details of the scanning process are maintained by the holding institution if not recorded in the description of the digitized map.

SELECTION

RESOURCE DESCRIPTION: Cataloging

IMAGE CAPTURE

Capture Hardware

RESOURCE DESCRIPTION: Structural Metadata

IMAGE LOADING and RETRIEVAL

As possible, given the size of source maps and the limitations of imaging equipment, image capture adheres to the standards promulgated by the Cornell Department of Preservation and Conservation (see Digital Imaging for Library and Archives, Kenny and Chapman, 1996). A Quality Index of 5 or better for visual images is required as possible.

Three types of images are created for all maps in the collection: TIFF master, JPEG thumbnail and SID zoomable image. Participating libraries create TIFF and JPEG images and submit them to FCLA, which subsequently creates the SID derivative. As an exception, the digital library facilities of both the University of Florida and the University of South Florida process their own SID files.

TIFF images are created as the direct result of scanning source materials (that is, as the native file format). TIFFs are archived as uncompressed electronic masters. Bit-depth is appropriate to the source and its anticipated use, and may be bitonal, 8-bit gray, 24-bit color, or greater. Color images are created and maintained in the sRGB color-space. Both hardware and images are calibrated and scanned to within the tolerances promulgated by the Library of Congress for the American Memory project. Images created from an analog film intermediary reflect the quality of the source microfilm. Nearly all TIFFs are imaged in-house. Solutions utilizing an analog film intermediary are usually vended to commercial services.

Guidelines for post-image processing of TIFFs varies from PALMM institution to PALMM institution. There is no shared aesthetic. And, even at a single institution, a particular aesthetic may not be applied uniformly. Most commonly, the scanning institution will created and archives a TIFF image with minimal post-image processing. The most aggressive of these minimal processes includes color balancing. More rarely and selectively, advanced processes are applied as digital "restoration". This process includes a number of image manipulation procedures based on knowledge of period paper and ink manufacturing. Generally, it is attempted only when a pristine off-print is required or the need for one is anticipated.

TIFF images are used to create JPEG thumbnails using Adobe Photoshop or Cerious ThumbsPlus in a batch executable process. The TIFF image is resized setting the width to 630 pixels and the height relative to width. Creation of SID files is a function performed by the LizardTech SID encoder software.

Capture hardware differs from one institution to another, but each institution generally employs a one image strategy. Scanning institutions avoid, wherever possible, stitching images together to reproduce a single map; image stitching is a particularly imperfect process when working with maps.

The Flatbed scanners used are various. The majority are highend color-calibratable scanners, with minimum 600 dpi native hardware optics. Among the best of these systems is the University of South Florida's Contex FSC 6040 Chroma wide format color scanner that can scan up to 800 dpi optical, 24-bit color, using the WIDEImage 2.2 scanning application. The unit can accept maps up to 40" in width. Image processing and final quality control applications vary as well. The majority of flatbed scanning workstations employ Adobe Photoshop, but JASC PaintShop Pro and ImageRobot are used also.

Two scanning institutions, the University of Florida and the University of South Florida operate planetary digital cameras for capture of oversized maps.

The University of Florida's equipment is a Phase One PowerPhase FX digital camera back with a 10,500 pixel by 12,600 pixel 24-bit color capture capacity. The camera back is mounted on a planetary ZBE Satellite universal scanning system (no longer manufactured), including three lens mount & bellows, camera stand, and automated control system for calibrated imaging. This scanning system has the look and feel of a commercial microfilming camera. A Rodenstock Rodagon 135 mm professional enlarging lens (f/5.6) with an AR-1 high aspect ratio filter is used for imaging oversized maps. The image capture area is illuminated by two daylight balancedfluorescent Videssence ICELITE 360 light banks. Maps are held in place during imaging by a vacuum easel. All of the images are captured by and processed on a Macintosh Apple G4 (1 GHz with 1 GB RAM) computer operating under OS 10 with OS 9 subroutines for optimal performance of Phase One imaging software. Final quality control is performed under Adobe Photoshop. And, LizardTech SID Workstation (GUI interface) encoder is used for the creation of SID images. The University of Florida also runs the LizardTech DjVu Workgroup encoder.

The University of South Florida's equipment is a PhaseOne PowerPhase digital camera back with a 7000 pixel by 7000 pixel 24-bit color capture capacity. The camera back is mounted on a Hasselblad 501CM camera, mounted on a SuperRepro copy stand. The camera is equipped with 50 mm & 80 mm lenses. The image capture area is illuminated by a Videssence Koldlite 120V (K110-255BX) fluorescent light kit. All of the images are captured by Phase One imaging software. Final quality control is performed under JASC PaintShop Pro and ImageRobot. And, LizardTech SID Workstation (command-line interface) encoder is used for the creation of SID images. The University of South Florida also runs the LizardTech DjVu Solo encoder.

Map images and their descriptions are loaded into the Visual Collections server at FCLA, which is an application of the XPAT search engine and Image Class middleware available through the University of Michigan's Digital Library Extension Service (DLXS). Map descriptions are stored as indexed SGML files.

In addition, persistent URLs referencing the server application are created by program and inserted into the bibliographic record describing the resource in the library catalog.