GIS

Recently I have been looking into the specifications for the Open Geospatial Consortium (OGC) Web Feature Services (WFS) that provide a standard interface between geographic information systems (GIS) for the transfer of geodata.

I've been starting to think about it in terms of using the Drupal web framework as a geodata store that can be used by any standards compliant GIS. Drupal can already be considered a Geospatial Content Management System (GeoCMS) so this seems like a natural extension to allow other systems to talk to it.

In GIS, the term 'layer' is usually used to group together geographic information relating to the same kind of feature, e.g. forests, places or roads. These are often stored in different files or different tables in a database. In Drupal the equivalent concept is a little more flexible and fine-grained. All of the information is stored in one place (with the ability to extend a basic piece of information with extra attributes) and can be filtered by any number of 'tags' that may be assigned to different pieces of information.

Using a WFS server as an interface to data held in Drupal would mean that systems would have access to any number of geographic datasets simply by combining tags to retrieve the data that they need.

I'm looking forward to putting more work into building up a spec for a WFS Server module for Drupal, and hopefully one day geographic information systems will be able to query Drupal for dynamic geodata, and even create, update and delete it as well.

Back at the end of last year I bought myself a relatively cheap GPS unit - the Garmin eTrex personal navigator. I had wanted one for a few years and frankly it felt strange having gone through two related degrees, being interested in the area, and yet still not owning one of my own. For a long time I had felt left out, not being able to take part in things like Geocaching, easily geotagging my photos or helping expand open source mapping databases.

For the first few weeks that I had the device, I spent some time working out what situations it would work under - from being in the open, to keeping it in my pocket, to being surrounded by trees, buildings and even inside trains - and what sort of accuracy it could achieve. Whilst doing that I was also building up my database of waypoints around Stuttgart.

Christmas time came, and it was time to head home for a short break. It was interesting holding the GPS up to the window on the plane, seeing the acceleration as we accelerated down the runway. This was all experimentation though, in the lead up to my main plan of action for when I got back to the Isle of Man.

I wanted to drive as many of the island's roads as possible, taking tracklogs as I went, to allow me to add them to Openstreetmap, the open source database of streets around the world. It has taken me quite some time in the weeks since, but I've finally mapped just about all of the roads I drove (or at least the ones where the GPS was tracking). You can see the result by zooming in to the Isle of Man on the site.

The mapping of the Island is nowhere near complete (it's mostly the southern end that I concentrated on), and now that I'm back in Stuttgart, I want to see if I can find people located in the Isle of Man with a similar interest in opening up this sort of level of mapping to the public. Anyone with a GPS (and computer connection) can help out by driving some of the remaining roads, or even fixing areas of the map that I've inevitably not mapped as correctly as I would have liked to have done.