Westward by Sea: A Maritime Perspective on American Expansion, 1820-1890

Digitizing the Collection

All scanning was performed by staff of Mystic Seaport, using a variety of scanners (listed below). The most appropriate scanner was used for each item. The objective was to capture images at a resolution that supported reference and on-screen study, not to replace originals. In general, printed text was captured as bitonal images while manuscript and pictorial items were captured in greyscale or color. However, manuscript materials scanned from bound volumes were captured as bitonal images because of limitations of the software associated with the overhead scanner.

The original items in this collection vary widely in size, from nautical charts to postcards. Therefore, rather than attempting to generate master images of a particular size, materials were scanned at a resolution of 300 or 400 dpi, with the objective of creating a fully readable master image. Likewise, service GIF images were derived from the master TIFF images by scaling down to certain percentages, rather than to a specified spatial resolution. Although the service images are of irregular size, the images of larger manuscript items are much more legible than if constrained to fit on a 640 x 480 screen.

Printed text pages were scanned at 400 dpi to produce better images for optical character recognition and then reduced to 300 dpi. Color images were produced at 400 dpi. Large format items, such as charts, were scanned at 300 dpi.

For service images for text and manuscript pages, the GIF format was selected since it is more suitable for text than the JPEG format. Most GIF images of handwritten material were saved in 6-bit grey rather than 8-bit to conserve storage space without decreasing legibility. Color images were saved as 6-bit GIFs. To make bitonal text images more legible, they were scaled down to 8-bit images with a high amount of dither. The standard procedure was to convert to 8-bit grey, scale down dimensions by a certain percentage with approximately 87% dithering, and save as a 4-bit GIF.

Objects from the Mystic Seaport Museum's Curatorial Department were first photographed and then scanned.

Further details on equipment and practices are provided below.



Archival Images

Service Images

Scanning Specifications for Archival Images

Creating Service Images


Transcription Rules

Optical Character Recognition (OCR)

File Storage

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