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Large format scanning specs

Page history last edited by Monica 5 years, 2 months ago Saved with comment

Notes for developing local standards for master images of large format scans (above 17 x 24 inches physical size).

 

 

Proposal for Local Standard

 

Scanning Specs

MASTER

TIFF Format, uncompressed, flat

24 bit depth

400 ppi

General file size  800MB - no greater than 1.5 GB

 

ACCESS

Use  JP2 format for Zoomable display 

see specs at https://digitalriceprojects.pbworks.com/w/page/49937056/JPEG2000%20Profile

 

Supporting notes

  • Embedding layers into TIFFs will greatly increase file size (more than double), so all final master TIFFs should be flat if processed using Photoshop or other imaging editing tool.

  • Since scanning at “real size”, use of 400ppi should be sufficient

  • Reasonable file size may be 800MB or less. Set maximum file size of 1.5GB.

    • the largest map scanned to date is around 1.2GB but this map is a composite (merged in photoshop) of 3 scans. Expectation is that most maps will be much less than 1GB

  • If file size is greater than 1.5 GB may need to resample using 5000-10000pixels at long side

  • Policy: No scans of Rice Campus buildings will be placed in the IR for security purposes per Lee Pecht.

 

Additional information

  • Local projects should develop a method for tracking file sizes for large scale images to estimate digital preservation storage needs. This should be reported to DSS once a year for budgeting purposes.

  • Some overly large files can not use adobe (Bridge or Photoshop) to embed metadata. In such cases, use EXIF tool (see below for steps).

  • tips for merging files, see Image editing tips  

 

 

 

Using Jpeg2000 lossless format as master

  • Benefit: Greatly reduce storage needs and related costs in the event of significant growth of large scale scans. This practice of using JPEG2000 as masters is currently being used at the Library of Congress, British Library and Wellcome Library.

  • Known issues with using JP2 format as master

    • loss of color profile info

    • Need special software to view/create JP2 files

    • Therefore not recommended to use JP2 as master format at this time.

 

 

 

Exiftool (command line tool)

 

Embed metadata

Can automate creation of unique metadata for individual files using *.bat file. Tip: Use excel to capture unique metadata and then copy/paste data in *.bat file and run from command line window.

 

basic command example [ref]:

exiftool -Title="This is the Title" -Author="Happy Man" -Subject="PDF Metadata" image.tif

 

This command embeds a title, author and subject (keyword field) into the TIFF file.

This command will create a backup of the original file if you do not use the; -overwrite_original switch, this means a duplicate will exist in the folder where the updated pdf is. From example above; a file named drawing.pdf_original will be created.

 

Using exif to confirm no layers

 

Practices at other institutions

On going activity. Monitor any mention of large scale scanning specs in the community. If new practices/methodologies are discovered that recommend different guidelines, we can re-evaluate our local practices at that time.

 

UNT

http://www.library.unt.edu/digital-projects-unit/standards#large-format-posters-and

 

Large Format (Posters and Maps) Above 17 x 24 inches (A2)

Image Types

Bit Depth

Color Space

Resolution (ppi)

Scale

File Format

B&W Maps/Posters

8-bit

Grayscale

5000 - 10000 pixels across the longest side

100% (1:1)

Tiff (uncompressed)

Color Maps/Posters

24-bit

RGB

5000 - 10000 pixels across the longest side

100% (1:1)

Tiff (uncompressed)

 

National Geospatial Program

Standards for Scanned U.S. Geological Survey Historical Topographic Quadrangle Collection

http://pubs.usgs.gov/tm/11b03/pdf/TM11-B3.pdf.

 

Highlights:

  • majority of the maps are scanned at 600 PPI.

  • [24bit] is a true-color image appropriate for high quality printing

  • The goal is to produce a GeoPDF with a file size less than 20 MB.

  • High quality viewing and printing also is a goal for the TIFF. Typically the TIFF maps will range from 500 MB to 1.4 GB, again depending primarily on the original map sheet size.

 

National Geospatial Program Standards and Specifications: http://nationalmap.gov/standards/index.html

 

Federal Digitization Initiative Still Image Working Group (8/2010)

http://www.digitizationguidelines.gov/guidelines/FADGI_Still_Image-Tech_Guidelines_2010-08-24.pdf

 

Highlights:

  • 400 ppi minimum for oversize documents, alternative minimum of 300 ppi (dependent on size of smallest character in document)

  • Resolution of 8,000 pixels across longest side

 

Stanford Large format and map scanning specifications

https://library.stanford.edu/research/digitization-services/labs/digital-production-group/capture-specs/large-format-scanning

 

Highlights:

  • Recommends compressed TIFF format. This may be an alternative to explore if storage sizes become non-sustainable

  • Recommends using JPEG2000 as access version

 

 

Suggested Metadata

 

  • Recommended to assign top level type terms, such as dc.type.dcmi=Image and dc.type.genre=maps, posters, architectural drawings (visual works),
    blueprints (reprographic copies). See list DCMI Type Mapping.
  • For subtype terms it is possible to create local elements to capture this info. Possible subtype terms might include: atlases, aeronautical, nautical, and celestial charts, bird's eye views, plans, sections and profiles, maps of imaginary places, aerial photographs, globes, relief models and other three-dimensional cartographic resources, etc.
  • Optional: may add physical description or map dimensions using dc.format.extent element
  • Recommended to include  dc.digitization.specifications to describe technical specifications of how an item was digitized and if master format is available. 
  • Note: actual file sizes and mimetype are automatically captured at the bitstream level upon ingest.

 

Related resources

 

DCRM(C): Descriptive Cataloging of Rare Materials (Cartographic). Rare Books and Manuscripts Section of CRL (2016) http://rbms.info/files/dcrm/dcrmc/DCRMC.pdf

Recent publication. Need to explore any possible local applications from these new guidelines.

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