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SUSHMITAH / btstack

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BTStack GPS Speed is jumping #133

Closed GoogleCodeExporter closed 8 years ago

GoogleCodeExporter commented 8 years ago 
Hi,

i've just purchased BTStack GPS and want to use it for track recordings with 
Harry's Laptimer Pro and a 4Hz Wintec GPS Receiver.
During the first tests, i recognized that the Speed is jumping around 
(2-10km/h). Then i tested Navigon and there is the same issue.
Also in the recorded data i've made, there are lateral G Forces on a straight 
track.
With Navigon i could see that when you stop at a traffic light, the speed 
remains at approx. 15-20km/h and one second later goes to 0 and have the 
correct and fixed GPS Location.

The following Video on Youtube shows the problem with a Qstarz GPS Receiver 
(probably 10Hz):
http://www.youtube.com/watch?v=FZjshKZHxms
Thats not my Video, its just to show the issue!

Original issue reported on code.google.com by lowora...@googlemail.com on 16 Mar 2011 at 4:47

GoogleCodeExporter commented 8 years ago 
any response ?!?

Original comment by lowora...@googlemail.com on 7 Apr 2011 at 9:43

GoogleCodeExporter commented 8 years ago 
hi. BTstack GPS currently receives and uses only the actual position from the 
GPS receiver. To provide apps with speed information, it calculates the speed 
based on the time and distance to the last point. That seemed to work fine with 
standard 1 Hz receivers and should be fine too, when you're driving faster. If 
you have more samples, the accuracy decreases (at least with this approach).

I was informed that many GPS receivers also report speed themselves, so I plan 
on using those values directly in the next update. If there are no speed NMEA 
sequences, calculating the speed from a point 1s ago and the current one might 
give better data, too.

Can you try to reduce the update rate of the GPS receiver (somehow) and see if 
that helps?

Original comment by matthias.ringwald@gmail.com on 8 Apr 2011 at 8:22

GoogleCodeExporter commented 8 years ago 
i will try with 1Hz but i would appreciate the implementation of the "receiver 
speed" information to use 4Hz instead.
Is there a release date for the update yet ?

Original comment by lowora...@googlemail.com on 8 Apr 2011 at 12:37

GoogleCodeExporter commented 8 years ago 
no ETA. but I'll look into BTstack GPS after the Celeste 1.0 update which 
should be out in a week or so.

Original comment by matthias.ringwald@gmail.com on 8 Apr 2011 at 2:39

GoogleCodeExporter commented 8 years ago 
the latest 1.6 release has a switch to limit updates to 1 Hz

Original comment by matthias.ringwald@gmail.com on 29 Nov 2011 at 10:00