A Place in History - Section 4.2

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 4: BASIC GIS FUNCTIONALITY: QUERYING, INTEGRATING AND MANIPULATING SPATIAL DATA
	4.2 Querying data As with all database systems, one of the core parts of GIS functionality is the ability to query the data. With GIS software there are two basic forms of querying: spatial and attribute. Spatial querying asks the question 'what is at this location'? This is often done by simply clicking on a feature and then listing its attributes. More complex spatial queries could select all the features within a box or a polygon, or ask 'what is near to this feature'? These more complex queries often require the use of buffering or overlay techniques as described later in the chapter. Attribute querying asks the question 'where does this occur'? If a user has a layer consisting of the locations of churches with various information about each church, an attribute query could select all the churches whose denomination is Catholic and then draw them with a certain symbol. The user could then query the database to select all Protestant churches and draw these with a different symbol to compare the patterns. There is much more on visualisation in Chapter 6, the purpose of introducing it here is simply to show how querying and mapping are inextricably linked.


	© 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.