National Geological and Geophysical Data Preservation Program

Digital Scanning Workflow

A scanning workflow can be developed, once similar materials are grouped together. Generalized examples are provided below for documents, reports, and similar items; large-format sheets and maps; and photographs. Scanning and preservation workflows should be customized to individual organization projects that are focused on end-user needs and long-term access, use, preservation, and archiving of materials.  

Digital Scanning Tips and Suggestions

Scanners should be allowed to warm-up to operating temperatures to stabilize the imaging light source intensity. While scanners with a LED light source are relatively stable in a short period of time (typically less than 5 minutes), scanners using a fluorescent tube may need to warm-up 15 to 20 minutes or longer (see scanner manual for instructions) to achieve stable light intensity. Use of a power conditioner (often combined with an uninterruptable power supply) with scanning equipment can help reduce light source intensity fluctuations due to variable electrical voltage and increase the life of the scanning equipment.  

Scanning equipment should not be placed in areas with direct sunlight or strong ambient lighting (particularly fluorescent lighting), because the ultraviolet radiation may degrade materials and lead to fading and damage. Potential external light penetration to the scanner sensor may result in poor quality scans. Scanning equipment should be placed on sturdy surfaces that are not subject to vibration from other equipment, furniture, or the building itself and away from significant dust sources.  

During the scanning procedure, care should be taken to prevent damage to the materials, such as tears, punctures, smearing, transfer of body oils (fingerprints), dust and dirt. Handling of materials with appropriate dust-free gloves is recommended. Scanning equipment should not be cleaned with common household glass cleaners, rags, or towels. Imaging glass surfaces can be easily scratched and damaged and are often costly to replace. Scanner imaging glass surfaces should be checked regularly for scratches or other damage that may reduce imaging quality. Photographic-quality lens cleaners or other items and cleaning methods recommended by the scanner manufacturer should be used.  

Whenever possible, preserve the original, unmodified scanned digital file in an uncompressed or loss-less compressed common archive format (TIFF, PDF) stored in an appropriate archival device, and use a copy of the file for subsequent processing, cleanup, and conversion to a distribution file. The original scan in digital file format provides the raw data, which may be subsequently reprocessed, eliminating additional rescanning and handling of fragile materials. 

Typical Digital Scanning Workflow

  1. Sort materials
  2. Clean materials
  3. Scan
  4. Process and clean up
  5. Create distribution files
  6. Archive original files

Documents and Related Materials

Documents, reports, letters, and similar paper items less than tabloid size (11”x17”) that are not fragile can typically use the same scanning workflow, depending upon the scanning equipment. If page sizes are similar, document feeders integrated into high-speed document-type scanners may be used. While labor intensive, traditional flatbed scanners can also be used, but require each page (or, side for double-sided documents) to be manually loaded and scanned.  

Document materials should be scanned into PDF format, a universally accepted document format that preserves multiple pages in one file, and enables embedded metadata and optical character recognition (OCR) analysis to create text-searchable files. The XMP metadata system within Adobe Acrobat can create and edit common and custom metadata fields in PDF files that are accessible by a variety of other software.  

Large-Format Sheets and Maps

Large-format sheets and maps, or those with page sizes greater than tabloid size (11”x17”), will require the use of a large-format scanner. Large-format sheet-fed scanners automatically feed the sheet through the scanner and care must be taken with sheets that have tears, holes, or other defects to prevent further damage.  

Aerial Photography

Aerial photography, commonly available as 9”x9” prints, but also available in other sizes, will require a tabloid-size flatbed scanner to scan the entire image. Scans of aerial photography should include the fiducial marks and any information around the periphery of the image, such as camera or acquisition metadata. Aerial prints should typically be scanned at a resolution of between 800 and 1000 dpi to preserve fine detail needed for stereo aerial interpretation. Aerial films are commonly available in roll format up to several hundred feet long, requiring specialized scanners and handling. Most aerial film should be scanned at a minimum of 1200 dpi, due to the presence of fine grain and high detail.