Computing, GIS and Archaeology in the UK

Firstly, if you’ve seen this post before, apologies. It got lost in a previous re-organisation of the blog and I thought it was worth re-posting…

You can get free contour data for the UK from the Scottish Mountaineering Club website. It’s based on public domain NASA data, cleaned up by the club and made freely available. It comes in garmin .img format, in several zip files, which roughly represent areas of the country. See their web page for an explanation of the areas.

Edit: Leszek has some great alternatives methods and options for data- check the comments.

1. To convert the img files to something (more) useful, the best programme I’ve found is gpsmapedit. You need to register it to get the full functionality. This costs 42 euros (umm, about 32 pounds at the moment) but allows you to use the programme on up to four computers.
2. In gpsmapedit, click “open” or “add” and load up all the img files you want to convert. Note that they will be merged into one big file so for the sake of your poor computer, choose only the areas that you need.
3. Go to file/export/mapinfo file, select level “0″, this includes the minor contours (down to 10m) as well as the major contours (100m)
4. When it has finished exporting, you can shut it down. If you’re using mapinfo, then skip to step 6.
5. In ArcGIS, crack open ArcCatalog, and load the “Arcview 8.x tools” toolbar. Move your mapinfo files to a location on your computer that has no spaces in it’s path name and a short path. No really, do. It will crash otherwise. Choose the “mif to shapefile” converter. Alternatively, you could do this with ogr2ogr. See the website for usage.
6. The resulting file (mapinfo or shape) is in wgs84 projection, with the height values in feet, so for use in a British National Grid environment you need to re-project it. The height values are in the attribute field “label”, so add another field for holding the converted height and use the tool of your choice to convert the values in the “label” column to metres.

Note that this data is good for broad-based terrain modelling only. If you need something more accurate you’re going to have to buy it…

If you have any alternatives to this method let me know in the comments!

There have been a thought-provoking series of posts about the relevance of the Ordnance Survey. It’s good that people are questioning the need for a national mapping agency, but I think the answer has to be a resounding YES. The OpenGeoData blog doesn’t.

To quote:

“Me, I just don’t care about the Ordnance Survey. It’s not “evil” or “immoral”, it just doesn’t matter. I think that Open Maps can do better, and I’m willing to put my money where my mouth is by working on Open Maps, but it’s not a crusade it’s just a superior way of working together and generating maps.”

Superior is an interesting choice of word in this context. It’s perfectly fair for OpenGeoData to think that Openstreetmap suits his mapping needs, but to call it superior, and to say that the Ordnance Survey is irrelevant is a little short-sighted. The Ordnance Survey, and any national mapping agency, have a responsibility far beyond creating maps for the general population to use to get from A to B, and I wonder if Openstreetmap honestly feel that they are ready to provide disaster response mapping, or have the resources in place to ensure that their coverage of the entire country is current to within one year or less.

I like Openstreetmap a lot, and really enjoyed the talk that Steve Coast gave at OKCon last weekend, and I think they have a useful place in the free data debate, but I don’t see them as a replacement for our national mapping requirements. In my opinion, pretending that they are simply dilutes the fight to change the Ordnance Survey’s licensing policy.