Sat-nav Accuracy And Calibration

October 20, 2009

Hello,

when I first got my car,I was impressed with the accuracy of the sat nav. Recently however, the accuracy has been quite poor.

Occasionally, when looking at the map, the green arrow (me) will be running parallel to the road I'm actually travelling on. More often however, the arrow can be around 30 yards out which makes the system almost useless when going round back streets. I' not expecting it to have the accuracy of a Storm Shadow ALCM however it *used* to be far, far better.

Has anybody else come across this or perhaps know a way to get it back on track?

Thanks for reading.

October 20, 2009

Hi,what is your device???.

We all have the same prob,it's mainly due to the satellites position in relation to the EARTH as this isn't perfectly round & it wobbles slightly on its axis.

With my tom tom 1 europe i have installed "tom tom home" on our lap top & i update it once a month-ish or before a specific trip as this resets it.

I hope this helps B)

October 20, 2009

there should be something in the manual about updating/correcting it - there is for my Avensis' satnav.

November 2, 2009

Thanks all, there seems to be something about calibration so will double check this - it's part of the TNS510 (off the top of my head).

It is very odd thoug, it was pin-point accurate then one day and since, it has been considerbly out.

Once I've RTFM word by word, I'll report back.

Cheers.

December 30, 2009

Thanks all, there seems to be something about calibration so will double check this - it's part of the TNS510 (off the top of my head).
It is very odd thoug, it was pin-point accurate then one day and since, it has been considerbly out.
Once I've RTFM word by word, I'll report back.
Cheers.

According to the TNS510 installation manual (available in the Toyota Techdoc website), it appears that the GPS antenna of the TNS510 is installed in the dashboard and this is a very poor location (it should be on the roof). This definitely is a source of loss of precision, and relocating the antenna on the roof should help (I haven't tried yet, but plan to do so in the future).

Another source is the fact that GPS devices need a clear view of the sky during several minutes (up to 30mins) before getting their best accuracy. This is because they need to download the current satellite positions from the satellite themselves (ephemeris/almanac), these files are broadcast by the satellites at a very low bitrate. And you need a clear view of the sky for this to work best. So if you want the best accuracy, leave your car with the GPS on during half an hour in a place where it has a clear view of the sky, and it should be better afterwards. Do this at least once a week because this data expires.

Hope this helps