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Inaccuracy of GPS

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By well0549, Senior Member on 18th May 2009, 11:14 AM
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Well i have a question.

When i use TomTom or IGO the position on the screen is always about 50 meters off to where I actually am.

So since IGO & TomTom Both have the same behaviour i guess i should look at the GPS module.

My old S730 was always spot on... when i looked at the screen and saw a turn on the left, there actually was a turn to the left.

Anybody knows how this can be solved ?
Last edited by well0549; 19th May 2009 at 12:41 PM.
 
 
18th May 2009, 12:44 PM |#2  
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My TD2 does not have this problem, perhaps there is an issue with your particular phone?
18th May 2009, 01:17 PM |#3  
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I thoght about it before and found out that it was not inaccuracy but the delay GPS chip needs to calculate your position. Do one test. Some time when you stop at a red light and you know you've waited for about 5 secs, check your position then. I believe it will be accurate then.
I noticed that some GPS's try to calculate your current position based on direction and speed you had few seconds ago. I found out about it one time when I waited at the red light in a long tunnel. Obviously there was no signal there, but when I stopped, GPS kept on showing that I was moving about 40MPH for several seconds before it finally showed lost signal message.
Some GPS's do calculate your position ahead of time and some don't.
18th May 2009, 01:27 PM |#4  
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Maybe it was because i had assisted GPS turned on...

If you do a search on AGPS LAG (ANY HTCPRODUCT WITH AGPS) then you will see enough posts that speciffically deals with this problem...

My old phone is SPOT ON with TT and my new 2 times faster phone is less accurate, and in a street with lots of turns, take a-lefts etc it's quite important to rely on the machine. And when the machine says turn left on the next corner, is that left the one i am currently at or the one 20 meters ahead from where i am now....

It should be just as with my old phone spot on
19th May 2009, 12:40 PM |#5  
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Well disabeling AGPS definitely works...

I am now about 20 meters behind all the time. This seems acceptable although I keep finding it strange that my older phone was way more accurate.....
19th May 2009, 12:55 PM |#6  
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you mean disable QuickGPS or disable AGPS in Advanced Config??
19th May 2009, 03:41 PM |#7  
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It is definitely a lag issue, not a precision issue: my TD2 internal GPS is at least as accurate as my Qstarz bluetooth GPS logger, and this one has a dedicated large antenna and good GPS chipset. TD2 sensitivity is also comparable, maybe even better inside building, and the time before locking a signal from coldstart is also comparable or better...

BUT there is a lag of maybe 30 m around 50 km/h in my car, and it is is indeed quite noticeable for driving directions...No big deal for me, as I do not rely on voice instruction but always have a quick peak at the screen (I was bitten by ambiguous instruction often enough in the past with other GPS system to have developped this quick peak habit ;) )..but this lag is indeed anoying...

I'd like to try the TD2 using the external GPS through bluetooth, if I find time to do it this WE I will post my conclusions...
19th May 2009, 05:43 PM |#8  
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Quote:
Originally Posted by well0549

Well i have a question.

When i use TomTom or IGO the position on the screen is always about 50 meters off to where I actually am.

So since IGO & TomTom Both have the same behaviour i guess i should look at the GPS module.

My old S730 was always spot on... when i looked at the screen and saw a turn on the left, there actually was a turn to the left.

Anybody knows how this can be solved ?

I use to have the same problem as you, so, I've tried the tweak referred in this post http://forum.xda-developers.com/showthread.php?t=514912 and it did the trick for me.
I use iGo8 and NDrive and the accuracy improved a lot, it's almost spot on, no matter what speed I'm driving.

Regards,
19th May 2009, 06:44 PM |#9  
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I was in my mates Audi TT the other day. He has the built in GPS in the dash board. I noticed there was as much lag as you see on an HTC device.

Also was in a car a few months asgo with someone who had a stand alone TomTom device and that too had lag.

Unless you're paying thousands of Dollars for millitary grade navigation equipment, i wouldn't spare the lag issue another thought.
19th May 2009, 06:49 PM |#10  
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Not long now ...
There's a bigger lag comming if the media are to be believed (and based on everything that comes from the tele, radio and newspapers these days - there're probably not - they can't even get the weather right)

http://news.sky.com/skynews/Home/Tec...y_Office_Warns
23rd May 2009, 10:44 PM |#11  
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"
Unless you're paying thousands of Dollars for millitary grade navigation equipment, i wouldn't spare the lag issue another thought."

Diamond1 paid 150 was spot on. No Lag. The speed indicator on tomtom was very accurate, not like on the diamond2 where it takes over 2 seconds to show a speed change. I am surprised that not many people have noticed the slow and inaccurate GPS performance of the D2.

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