GIS File Formats: how do we distribute data?

Wednesday, 1 November, 2006

One of the other discussions that cropped up at the GRADE meeting was file formats for spatial data in relation to repositories. In the back of my mind I’m also thinking about the Journal of Maps as there is interest in publishing data. So what file formats do we use for data distribution, particularly bearing in mind the need for ready accessibility as well as preservation for future use. You have your ECW, IMG, SHP, TIF etc etc. What is good? Why? Will it work? What doesn’t it support?

In terms of formats we are really talking about raster, vector and attributes. At the lowest level these are all that are need to import data for use in any processing system. But that is all they are; low level. There is no preservation of symbology for instance. I think this is a good starting point (and its where I am going to start!), but I’m happy to be contradicted.

So, what formats?
Vector
Well SHP is good because its well understood and there are plenty of tools to deal with them (and I think its important that support from projects like GDAL/OGR is maintained). OK it’s not topological but very flexible. The same case could be made for DXF as well; is this worth including?. On the topological front E00 might well be worthwhile (in that its simple). How widely supported is it? Are there any other formats worthwhile considering??
Raster
GeoTIF is really the dominant player for open formats and JPG should be included because it is also a standard photographic format (along with the EXIF data).
Attributes
So that deals with the spatial side, we then have attributes. Is DBF the most apt? It is well supported. It might also be useful to add CSV for tabular data, particularly as its ASCII based.

What I haven’t mentioned here at all is GML. It is still very early days with limited support, but this has the potential to be the way forward. Even in the standard XML arena limited inroads are being made, although with both OpenOffice and MSOffice supporting it in office apps things could change rapidly.

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