walking sideways?

[gotskov]

Hi There.

I got the following hard/software

HP Ipaq 2210
Leadtek cf gps 9534
Tomtom navigator 2 Skandinavia

Sometimes when im walking with it, the blue arrow, which tells med where i am and in whích direction im going, shows a wrong direction. Its pointing to the left. Exsample: Im walking north but the arrow points to west.

How can that be? Also some time i get a wrong position (up to 200m).

Is cf leadtek 9534 very bad or is it normal?

Links to leadtek specs
http://www.leadtek.com/gps/gps_9534_1.html
http://www.leadtek.com/gps/gps_9534_2.html

[Dave]

The main reason is TomTom isn't designed for walking, although you can use it for walking. What happens is the long/lat data it gets back, it will compare several of these together to see if these figures are both increasing, both decreasing, one increasing and one decreasing and vice versa. It can then compare these over a period of time (seconds) and then try and suggest which direction you are pointing in / moving in. It doesn't always work, mainly because GPS isn't 100% accurate, there are multipath errors when around tall buildings or under trees and this can cause an offset, and sometimes you will find the pointer pointing in the wrong direction.

Another thing to check is that you are using NMEA, try using the TomTom NMEA 0183v2 driver and set the baud rate to 4800 or 9600 and see if that makes a difference. If you are in SiRF mode, this can also cause a problem with TomTom.

Wrong positions can be caused by multipath errors, or low sats. If you have 4 or less, then you could be quite far off. If you have 10 or 11 sats then you'll get a much better position. 7 sats is usually an average most see.

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