A Place in History - Section 3.7

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.

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	A place in history: a guide to using GIS in historical research CHAPTER 3: ACQUIRING SPATIAL DATA
	3.7 Raster-to-vector and vector-to-raster data conversion The holy grail of spatial data capture is to be able to scan simply a map and then automatically extract point, line and polygon features. This is called raster-to-vector conversion, but it has not proved easy to implement. Some systems claim to be able to do this but the process usually requires a large amount of user interaction. Even then it can be inaccurate: for example, lines can pick up a stepped effect as a result of following the underlying raster grid pattern. Vector-to-raster conversion can be more successful, but care still needs to be taken. Many software packages include routines that allow both of these conversions to take place, but many also make exaggerated claims about the potential accuracy of the routines. Before committing to a major purchase, or major investment in time, it is well worth checking the results first rather than believing the sales pitch provided by the software company.

	© 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.