This is another one that I did myself. There was no river mile numbering system that I could find on the Internet. So I made one up starting at the so called “Yantlet Line” near the river mouth to the Thames Source. The Yantlet line dates back to 1300 or so. It was the limit of of the City of London’s jurisdiction over the river for centuries. (See: http://en.wikipedia.org/wiki/London_Stone_%28riparian%29)
Actually, the Thames Source is somewhat controversial as well. The true source is actually along another tributary to the north. No matter. The river isn’t navigable upstream of Cricklade. That is where my friends will begin their journey. BTW, that trip was supposed to happen this fall but has been postponed to March of 2013. I figured I would post the map now so that perhaps someone else might find the line and points of interest useful. It’s kind of a work in progress. More will likely be added to it after the first of the year.
The Thames National Trail is also on the kmz file. That is a footpath the runs from the Thames Barrier to the Thames Source. In the lower reaches there are actually two paths, one on each side of the river.