Changes to GPS Accuracy testing

I've made two changes to the way I calculate GPS Accuracy scores. The first change is that the overall accuracy is now a combination of Precision and Trueness, which changes the relative order slightly, but the underlying detailed results remain the same.

The second change is that I'm now calculating Precision rather differently. Instead of treating every lap equally, I now group them by the segment of the course, calculate Precision for each segment, and then combine the results. This is to offset the problem that some watches have a slightly higher percentage of their lap data for different areas, mostly due to me failing to hit the lap button occasionally. This does change the underlying results, with all scores increasing slightly due to the underlying math. This also changes the order, which is why I made the change. 

For the updated results, see GPS Accuracy and for details on my methodology see GPS Testing Methodology