Positioning Accuracy

jeffcooper · Occasional Visitor Joined: Mar 04, 2005 Posts: 32

I have noticed in the hardware forums a few mentions of TTM showing position on the road slightly delayed - can we get some comments on this - as I'm not sure which part of my setup is causing it - TTM, Nokia6600, BT338, or is it just the second delay that all NMEA receivers have when talking to the host device? It's one of those annoying points that it would be great to get to the bottom of!

I don't think it's got anything to do with actual GPS accuracy, since it's consistently 50 or so yards back.

lbendlin · Posted: Sun Sep 25, 2005 11:47 pm Post subject:

There should not be a delay. Do you see the same with other programs?

50 yards is still within the standard GPS threshold, although the BT-338 should give slightly better positioning accuracy.
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Lutz

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jeffcooper · Occasional Visitor Joined: Mar 04, 2005 Posts: 32

I tried Route66 this morning - the same delay is apparent, so I'm wondering wether it's a phone thing - is it just not quick enough?

lbendlin · Posted: Tue Sep 27, 2005 3:09 pm Post subject:

Sounds like it.
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jeffcooper · Occasional Visitor Joined: Mar 04, 2005 Posts: 32

On looking a little more closely I have discovered a couple of points that are of interest.

1) TTM definately does some work on the coordinates that it's getting - to smooth them out or whatever, but this I suspect answers those situations where it gets it very wrong - wrong road after a turn off etc

2) and this is the stupid one! - I realised that the Blue arrow that is supposedly the car/you, is at that scale about 75-100 yards long. Doh. If you look at where the very sharp point of the arrow is on the map, this is much closer to being exactly where you are on the road.

If the TTM programmers used the worked on GPS pos as the place for the tip of the arrow on the screen, and then drew the arrow back from it, that would explain things, and as a programmer, I can honestly see how that could happen - but if I'm right, then perhaps in the next release, the centre of the arrow could be the GPS pos!

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