The GIS is an incredibly flexible tool. It enables all sorts of data (gathered for all sorts of reasons, to all sorts of undefined standards) to be brought together, shared, analysed and abused. How we wish to see our data displayed may not be appropriate if that data is displayed against third party data with colour and symbology conflicts that may arise.
Moving towards standardising the cartographic representation of graphic elements (linework, point symbology, area features) within a GIS (such symbology exists for geological mapping) is a presentation issue. With style sheets or legends in a GIS, all you are really standardising is the representation of the underlying data. Legends do not address fundamental issues such as the interpretation or quality of the information. It is with this data, where standards should first be defined.
What we really should be asking is how much standardisation should exist between datasets commissioned from external sources. Are they simply a digital record of a particular event, be it an excavation or a field survey, associated with a site record? Alternatively we could apply controlled terminology to information describing the character of the event so that the limit of excavation (as opposed to trench edge, or edge of trench etc.) is used consistently between contractors. This would enable key information to be plotted systematically in the GIS but not affect how the detailed archive was structured within the project. Or should we be more ambitious and demand the ability to search across datasets? If digital archives are organised systematically, the GIS could provide detailed spatial analysis of excavation archives enabling the user to retrieve for instance all post-holes that produced flint from prehistoric excavations.
We should address issues concerning input of data including orginal data capture standards including documentation (metadata) accuracy and precision, data migration from CAD to GIS and between GIS systems.
How do we share data? Current supply formats include industry standard shape files and MapInfo export formats, dxf and various types of database. Future developments will impact on the GIS industry. Already we have GML on the horizon and as database developers like Oracle become involved, exchange mechanisms to serve the wider GIS community will inevitably adapt to meet their demands.
There are also longer term issues concerning how we store and maintain our data which need to be addressed (though perhaps not by this discussion forum).
Peter McKeague
RCAHMS
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RCAHMS
(The Royal Commission on the Ancient and Historical Monuments of Scotland)
John Sinclair House, 16 Bernard Terrace, Edinburgh, EH8 9NX
Tel: 0131 662 1456
Website: www.rcahms.gov.uk
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