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GIS Guide to Good Practice
Section 5: Documenting your GIS Data set

5.2 Levels of documentation

In documenting something so complicated as a Geographic Information System, it is possible to enter into great detail, and record everything from the data sets comprising the GIS to the sequence in which individual commands were applied to the data in order to produce your current system.

As with most things, there are situations in which great detail is required, and others where a more slimmed–down level of recording might be more appropriate. It is generally up to you as creator, maintainer, and primary user of your data to decide how much documentation is justified, and to select a suitable level for the language of your documentation; is 'cleaned coverage' appropriate, for example, or is your situation such that the more expressive:

'Using the Arc/Info clean command, tidied up the new pottery layer in order to remove errors introduced whilst digitising from the paper map. The command was

clean pottery # # # poly

is more suitable? The former has implications for decreasing the interpretability of your documentation, whilst the latter has implications for the effort required in producing this level of detail.

In documenting data which are to be made available to others, it is often necessary to describe things more clearly — and with a greater degreee of contextualisation — than is normally the case for internal use.

5.2.1 'Documentation' versus 'Metadata'

This guide, and many other documents distributed by the Archaeology Data Service, talk at length about a concept labelled as metadata. The term itself is a piece of jargon, but it serves as a useful label which is increasingly understood both within archaeology and in the wide world outside our discipline.

Several definitions are offered for metadata, but one which might usefully be given here is that metadata is the means by which your data are transformed into information, interpretable to and re-usable by those other than yourself. In other words, metadata is a label for the extra details associated with any data set which enable someone else to place them into some form of context. Metadata might include information on the computer format in which the data are stored, the area of the country they relate to, etc.

Metadata in its widest sense may be considered all of the documentation conceivably associated with GIS data, but the ADS simplifies things somewhat by using the metadata label only to apply to metadata used for resource discovery. As such, information suitable for entry into the ADS catalogue itself, and which can be used to facilitate the discovery of your data by others, can be thought of as metadata, whilst the information you provide which helps people to use your data after they have accessed it may be thought of as ancillary documentation.

5.2.2 So... how much is enough?

Well, it depends... If you are documenting data for your own internal use, you are of course free to use as much or as little of what is recommended here as you like.

If, however, you are preparing data for deposit with the ADS, then you will need to comply with the guidelines in section 5.4 on Dublin Core metadata, as well as supplying sufficient documentation (discussed in section 5.3) to enable re–use of your data. Where your data are particularly complicated, ADS staff may recommend other — specialised — documentation to accompany them, and will hope to enter into dialogue with you at an early stage in order to define this.

At any stage during the documentation process, ADS staff are available to help in clarifying these guidelines, and to aid in interpreting their generality in the context of your specific requirements and data.


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Archaeology Data Service
© Mark Gillings, Peter Halls, Gary Lock, Paul Miller, Greg Phillips, Nick Ryan, David Wheatley, and Alicia Wise 1998

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