Position Lag On Gps Units.

[scotster]

I am sure this is a common question so sorry for asking it again.

 

I just got an Explorist 600 and am suprised at how far behind it can show my position when doing around 15mph on my mountain bike. Stationary the unit will be very accurate with a good lock in open country but it can up to 30m-50m behind me whilst moving...

 

Is that normal? Can I improve it somehow?

 

Will the size of the Topo map I am using affect this (currently only 10 Meg).

 

Thanks, Scott.

[+Pelamore]

IMO, several things can be at work here.

1- Most GPSr have a radius of accuracy. This can be from 5 feet (I don't trust that though) to 30ft or even more. It updates your position at regular intervals, if 2 locations don't agree, it "Jumps" to the new one. If the first location is 30 feet behind your actual position, and the new is 30 feet in front, you get a 60 ft jump.

2- Tree cover or even street lamps can interfere with the signal. If it looses the satellites for a few seconds, it won't tell you, just jump to the new position when it gets one.

3- Each position is a complicated Mathematical equation. Depending on how often your unit does this equation you might "Jump". Check for "Power Saver" options that may be reducing the Calcualtions per minute to save batteries.

4- Heat. Computers, and GPSr's are small computers, they slow down in heat.

5- I guess it's possible that a low res map might have limited "Spots" for the unit to say you are at. You would have to experiment with this to find out.

6- If you are tracking your position through a "Track Log", remember that your unit might be rationing the postions. Dropping a track point every 150m for example.