Originally Posted by
Pop N Wood
Unfortunately not true.
It is update rate. the GPS only records a position every so many seconds (or fractions of one). It computes distance traveled by taking the distance between the two waypoints and dividing by time to get speed. If the GPS records one waypoint at the entrance to the circle and one at the end, well it doesn't take a math genius to figure out it won't compute an accurate distance.
I suppose people are talking about the turning circle at the end of the cul-de-sac.
It would have to be a quite small turning circle or you'd have to be going very fast.
At 3 mph, one moves 4.4 ft per second. A 100 ft cul-de-sac would produce about 50 measurements (1/sec).
At 10 mph, one moves 14.7 ft per second. A 100 ft cul-de-sac would produce about 20 measurements (1/sec).
At 15 mph, one moves 22 ft per second. A 100 ft cul-de-sac would produce about 9 measurements (1/sec).
The average car length is 15 feet, A really-small (not realistic) turning circle would be 3 car lengths or 45 ft. They are more likely 2-3 (at least) times as long.
There should be more than enough points to get a fairly accurate measurement of distance.
The distance might be off but not by that much.
Anyway, we have no idea at all how far off it supposedly is!
Originally Posted by
Pop N Wood
The Garmin I have varies how often it records the waypoints saving space on the memory card.
The device measures at the same rate but, with the "smart recording", it doesn't save the new point if it's not significantly different from the prior point. That is, if the location or time isn't much different.