A Place in History - Section 3.2

The right of Ian Gregory to be identified as the Author of this Work has been asserted by him in accordance with the Copyright, Designs and Patents Act 1988.

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	A place in history: a guide to using GIS in historical research CHAPTER 3: ACQUIRING SPATIAL DATA
	3.2 Scanning maps to produce raster data Scanning is a relatively straightforward process in which paper maps are placed on a scanner and a raster copy is produced. Smaller scanners are often relatively inexpensive; however, larger ones suitable for large map sheets are still expensive. The spatial resolution of the scanner, usually expressed in dots per square inch (dpi), and its spectral resolution (the number of colours it can distinguish), must be borne in mind, as this will affect the accuracy of the resulting data. Converting from the resulting scan to the type of raster data described in the previous chapter will require a certain amount of post-processing. If the source maps are relatively simple and focused on a single theme, such as land-use or soil type, this may be quite straightforward, whereas converting from more complex sources can be very time consuming.

	© Ian Gregory 2002 The right of Ian Gregory to be identified as the Author of this Work has been asserted by him in accordance with the Copyright, Designs and Patents Act 1988. All material supplied via the Arts and Humanities Data Service is protected by copyright, and duplication or sale of all or any part of it is not permitted, except that material may be duplicated by you for your personal research use or educational purposes in electronic or print form. Permission for any other use must be obtained from the Arts and Humanities Data Service. Electronic or print copies may not be offered, whether for sale or otherwise, to any third party.