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How to adjust tracklogs?

 
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guest



Joined: 08 Oct 2006
Posts: 5020

PostPosted: Sun Jun 29, 2008 1:23 pm    Post subject: How to adjust tracklogs? Reply with quote

Hi,

I have problems making a tracklog for use at OpenStreetMap.org. They require it to be uploaded in the GPX format.

The problem is that the traces is all over the place, and don't follow my path. At least when I compare it to the Yahoo satelite photo background. I have not found any tutorials on the tracklog feature, so I have tried a little myself. Until now, I have edited the "GPX dt (s)" from 60 to 5. I guess "(s)" means seconds (??).

Here is my settings:
GPX 1.1

GPX Options:
Marked "log only valid"
Not marked "log gsm info"

GPX dt (s):
5

GPX ds (m):
-1

Is there anything more I should adjust? I should mention that I both have used a scooter and walk when I have made tracklogs.

Also, is it normal that the tracklog don't follow the path, so you always have to adjust it afterwards? If yes, isn't that a problem when tracklogging new paths (don't have anything to compare it with)?

PS! I use a Sony Ericsson C702 (internal GPS). Could it be possible that this is not as good at this as stand-alone GPS's?

Thanks!
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Dubs



Joined: 21 Jun 2008
Posts: 5

PostPosted: Sun Jun 29, 2008 5:16 pm    Post subject: Re: How to adjust tracklogs? Reply with quote

guest wrote:
PS! I use a Sony Ericsson C702 (internal GPS). Could it be possible that this is not as good at this as stand-alone GPS's?


I can't answer your question in general, but I can say, that I made a long trip to Danmark yesterday and that I got a nice tracklog (car and by foot) via the c702 (default settings). The c702 need some time to get a fix, and it is a bit more sensitive by finding sats (compared to my BT mouse), but its working flawlessly for me.

cheers,

Dirk
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Erik



Joined: 29 Jun 2008
Posts: 3
Location: Oslo, Norway

PostPosted: Sun Jun 29, 2008 6:59 pm    Post subject: Re: How to adjust tracklogs? Reply with quote

Dubs wrote:
guest wrote:
PS! I use a Sony Ericsson C702 (internal GPS). Could it be possible that this is not as good at this as stand-alone GPS's?


I can't answer your question in general, but I can say, that I made a long trip to Danmark yesterday and that I got a nice tracklog (car and by foot) via the c702 (default settings). The c702 need some time to get a fix, and it is a bit more sensitive by finding sats (compared to my BT mouse), but its working flawlessly for me.


Thanks, nice to know that the C702 is doing well Smile

The problem for me, as I havent used a GPS before, I don't know what a "nice" tracklog is. Is it that it follows your path exactly, so that if you place a Yahooo map under, it will follow the road?

Yes, it takes about 5 minutes (sometimes more) to get a signal/fix.

Here is a pic of one of the tracklogs I made (a small walk, GPX dt (s) set to 5):

I should note that I wasn't drunk Smile

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DaBear



Joined: 15 Apr 2008
Posts: 19

PostPosted: Mon Jun 30, 2008 9:08 am    Post subject: Reply with quote

Well, accuracy of GPS is something between 10-20m, so your track could be 40m off the actual position. The yahoo satellite images can't be considers as accurate, too. As each photo covers a large area and because of the height of the camera, only points which are vertical beneath the camera are exact. Points at the borders of the images are distorted, sometimes you can see this by flipping shadows, or high buildings which seem to be tilted...

hope that explains a little...

For openstreetmap use your tracks as hint, an draw straight lines through them. If you overlay multiple tracks of the same area, or walk a street once an each side, you can use the average of those tracks...
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Cactus



Joined: 14 Dec 2007
Posts: 214
Location: Fife, Scotland

PostPosted: Mon Jun 30, 2008 9:31 am    Post subject: Reply with quote

It's also possible that the buildings are distorting the satellite signals.
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Dubs



Joined: 21 Jun 2008
Posts: 5

PostPosted: Mon Jun 30, 2008 10:25 am    Post subject: Reply with quote

DaBear wrote:
Well, accuracy of GPS is something between 10-20m, so your track could be 40m off the actual position.


Naa, this is not true. Accuracy is much better. Anyway, heres a track in Google Earth from last weekend (by car and by foot), there are some minor flaws, but overall its ok I think.



cheers,

Dirk
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Erik



Joined: 29 Jun 2008
Posts: 3
Location: Oslo, Norway

PostPosted: Mon Jun 30, 2008 11:13 am    Post subject: Reply with quote

DaBear,
Thank you for informative info, that would explain a lot. Then my (above) tracklog wouldn't be too bad, compared to others. Also a very good tip regarding OpenStreetMap.

My main plan is to make tracklogs in the backcountry, where there is no roads or buildings to recognice (Yahoo map). I will then walk the pats more then once, and draw a line between the tracklog lines.

Cactus,
Thanks!

Dubs,
SPAM, that looks much more precice then mine. Do you always get so good tracklogs? Is there any difference, in quality/accuracy, between the Google Earth and Yahoo maps?

Does anyone have any coments on the earlier mentioned tracklog settings?

Also, there is a option called "GPX Options" where we can mark "log only valid" (marked) and "log gsm info" (unmarked). Does the latter make use of A-GPS (supported by my phone), ie using GSM signal transmitters to calculate the position?

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kruch
Site Admin


Joined: 02 Jul 2006
Posts: 5673

PostPosted: Mon Jun 30, 2008 6:58 pm    Post subject: Reply with quote

Erik wrote:
and "log gsm info" (unmarked). Does the latter make use of A-GPS (supported by my phone), ie using GSM signal transmitters to calculate the position?


No, it adds current cellid and lac to recorded pt.
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Erik



Joined: 29 Jun 2008
Posts: 3
Location: Oslo, Norway

PostPosted: Mon Jun 30, 2008 7:15 pm    Post subject: Reply with quote

kruch wrote:
Erik wrote:
and "log gsm info" (unmarked). Does the latter make use of A-GPS (supported by my phone), ie using GSM signal transmitters to calculate the position?


No, it adds current cellid and lac to recorded pt.


Ok, thanks!

What about adjusting the "GPX dt (s)"? Is it correct that the lower the number, the faster the tracklog updates? Like if it's set to 5, it updates every 5 seconds. And, if this is correct, is it useful when riding a scooter/car for example? Or, is it best to leave it to 60 (default)?

Sorry, that was many questions...

BTW, I understand that you made this software Kruch, I find it very useful. Great work! Very Happy

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kruch
Site Admin


Joined: 02 Jul 2006
Posts: 5673

PostPosted: Tue Jul 01, 2008 8:28 am    Post subject: Reply with quote

On bike / in car I use GPX tracklogs with default settings, because I'm only interested to see later where I turned during the trip. The dt means "record a location at least every N sec", ds "record a location at least every N meters", but TB records locations where it detects turning on its own.

And for hiking, when I want "high precision", I use NMEA logs.
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