How accurate is a GPS Running Watch?

There are many times I wondered what exactly is a watch that is running with GPS and can really tell how fast and far? As a case study, we can look watch two of the most popular is the Garmin Forerunner 305 and 405

Both the Forerunner 305 and 405 have an integrated, highly sensitive SiRF Star III GPS receiver. Frankly, I have no idea what thesemeans. But I can tell you that both are incredibly accurate.

Garmin watches have a feature where they tell you how many satellites are in, and the prosecution, as you do. On this same screen will give you an accurate range. Typically, this area is between 10-20 meters more or less. This means that satellites orbiting the earth and know that you are in a circle 30-40 feet in diameter. The worst case would be 40 feetonly a few seconds to run, then the clock was off by only a few seconds.

Application, several hundred miles with a Garmin to check the mail, I found very little rhythm or inaccuracies in its removal. When I run the same routes, have with the Forerunner, it beeps constantly on the mile markers in exactly the same point along the route. On my regular cycle, 5 miles, I learned to wait for the buzzer signaling the beginning of my last mile, as I amHappen to the third power pole on the right.

As a further test, my companion and I both had a race Forerunner Clock 20 km training run. As we finished the race, we found that the distances of the GPS clocks were almost identical. At 20 miles, there were less than one twentieth of a mile gap between the two clocks.