How accurate is a GPS?

[pezulu]

If GPS is so accurate why do Garmin choose to use the wheel sensor above the GPS data on their new products?

 

The wheel sensor is to determine the size of the wheel you are using, and from there calculating the distance you have travelled.

 

Remember that a GPS like the Edge 500 does not have any onboard maps, so it can't calculate where you are on a map. It takes your coordinates in relationship to the 4 satellites it has locked on. Using them, and using the circumferences of your tyre, it can work out what your speed it, how far you have travelled, and all the other goodies that you see on your unit.

 

Once you have downloaded the raw data to a mapset using Mapsource, Garmin Connect or whatever your preferece is, you get a route on a map.

 

I am referring this question to www.garmap.co.za for a more informed answer, and will revert.

Edited December 26, 2010 by pezulu

[chris_w_65]

The wheel sensor is to determine the size of the wheel you are using, and from there calculating the distance you have travelled.

 

Remember that a GPS like the Edge 500 does not have any onboard maps, so it can't calculate where you are on a map. It takes your coordinates in relationship to the 4 satellites it has locked on. Using them, and using the circumferences of your tyre, it can work out what your speed it, how far you have travelled, and all the other goodies that you see on your unit.

 

Once you have downloaded the raw data to a mapset using Mapsource, Garmin Connect or whatever your preferece is, you get a route on a map.

 

I am referring this question to www.garmap.co.za for a more informed answer, and will revert.

 

Take note, if you have no speed/cadence sensor then the GPS unit has no trouble tracking speed and distance from the sattelites. Perhaps not quite as accurately though.