The foundation of the article is mis-directed at best. It concentrates on how the GPS is "wrong" and that differenct GPS units are "wrong" to different extents. In fact, what is happening, and which is briefly mentioned, is that the GPS is being used in a wrong way. GPS navigation is extremely accurate and is used in aviation, shipping, military guidance, surveying, etc. But, like all tools must be used correctly. By the way Google Maps is not a suitable reference if a person wants To The Foot accuracy.
In that regard instead of following the time honored Forum practice of arguing the point I suggest that if you are really interested spend some time researching in the areas I mentioned. There is a wealth of material available.
In the end I'll bet you come to the conclusion that for cycling speed and location the 500 gives perfectly adequate data.
People don't tend to criticize wheel speed sensor accuracy because it is seldom evaluated. But, once through the setup and you'll see it has its' own problems.
Me? I've found that over the typical 30-60 mile routes I ride there is an insignificant difference between my 705 GPS input reading and the reading from the wheel speed sensor input.
Last edited by HawkOwl; 12-22-11 at 03:00 PM.