Dr Mike J Smith
DMT Meeting and themes
So the reason for going to the US was to attend DMT07 which is principally aimed at geologists and cartographers from state geological surveys, although this year there were representatives from the UK, Czechoslovakia and Japan. What I hadn't appreciated was that whilst there is the overarching United States Geological Survey, much of the geological work is done at state level. As a result there are 50-odd mini countries all doing things slightly differently with different levels of resources. At the federal level the USGS also has to undertake topographic survey as well. In terms of resources some states (e.g. Illinois) have over 200 staff, others have less than 5, whilst some states (e.g. Hawaii) don't have a survey! So all in all its an interesting dynamic.
And standards were very much a theme at the conference, with a desire to go to an entire end-to-end digital work flow, incorporating PDAs/laptops in the field through to map output using ArcGIS or Illustrator. To that end one of the groups has been working on "ArcGeology" an ArcMap data model (that has interested ESRI). Whilst geological maps present points, lines and polygons, polygons are actually inferred from point and line data. The data model therefore only stores points and lines at a primary data level, with all polygons being generated (using the points/lines to poly command). Any changes to the primary data requires new polygon creation. I thought this was a nice solution and echoes some ideas on data models in GIScience at the moment (e.g. Goodchild et al, 200X).
Another major thread of the conference was data transfer, with a particular focus upon conversion between different ontologies. GeoSciML is an XML schema currently in development that aims to address this issue. However this stores data as points, lines and polygons, with no transfer of cartographic detail (e.g. line weight, colour etc). This is clearly in contrast to the ArcGeology data model and we are potentially seeing the loss of geological information at either the data model or data transfer stage.
The final key in this digital workflow relates to 3D. Geology is more than representing the surface geology on a map, hence the reason there are often cross-sections. The map authors will have some kind of mental 3D model for the structure of an area, so the 2D paradigm is actually not appropriate. What is needed is a way of capturing this 3D information digitally so that it can be appropriately modelled, something that Ian Jackson (BGS) really brought home. He suggested that a move to define a data model for ArcMap may well be 5-10 years too late as it is purely 2D.
So whilst DMT is about digital mapping and cartography, this year it has demonstrated how subjects still struggle with modelling their subject, 25 years after GIS became a commercial product.