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Old 02-05-2019, 02:21   #1
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opencpn gps jumping

Dear all,

I'm running opencpn on a new Samsung TAB s4. Recently I've had issues in Brittany France with a jumping position (see screenshot).

I know that there is a thread for this kind of issues. But I did not understand and cannot figure out what they were talking about.

I am using the internal GPS of the tablet exclusively (no AIS data coming in either). It has GPS GPS + GLONASS, BEIDOU, GALILEO (from tech documentation). My doubt now would be that one of the systems is not working well in the west of France (Beidou?). But how could I filter out these?

With other software the GPS works just find (only used google maps so far). No jumping here.

Do you have any suggestions for a fix?

Cheers
Holger
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Old 02-05-2019, 05:01   #2
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opencpn gps jumping

Most likely I think a GPS issue and likely due to poor satellite reception / geometry.
Try taking the laptop outside if and when it starts this and see if it stops.

I have much better luck with a quality Bluetooth GPS and leaving it in an area where it gets good reception, than anything’s built in GPS myself.
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Old 02-05-2019, 07:36   #3
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Re: opencpn gps jumping

Thanks for you remark.
It was a composite boat. The roof should not have so much influence on the GPS signals. As long as I remember there were always three green bars on the GPS icon. And the conditions were not like bringing the tablet outside.
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Old 02-05-2019, 08:53   #4
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Re: opencpn gps jumping

Search on Jumping GPS in FAQ
https://opencpn.org/wiki/dokuwiki/do...r_manual:faq&s[]=jumping&s[]=gps#jumping_gps
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Old 02-05-2019, 09:59   #5
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Re: opencpn gps jumping

Quote:
Originally Posted by roede View Post
....
I am using the internal GPS of the tablet exclusively (no AIS data coming in either). It has GPS GPS + GLONASS, BEIDOU, GALILEO (from tech documentation). My doubt now would be that one of the systems is not working well in the west of France (Beidou?). But how could I filter out these?....
I'd use the NMEA debug window to check what's coming in to OCPN. If you device is sending individual sentences for each GNSS system, see the copied text below, you can filter out one at the time in OCPN connection properties. If your device is already combining different systems position to one GNxxx there's not much to do in OCPN more than check you've the Options->Display->Advanced-> "Chart rotation averaging time" set to at least 15 sec.
Håkan
Quote:
According to the NMEA 0183 protocol, the Talker ID serves to define the navigation system(s) used for the reported position coordinates. If only GPS, GLONASS, GALILEO etc. are used for the reported position solution the Talker ID is GP, GL, GA etc. and the errors pertain to the individual system. If satellites from multiple systems are used to obtain the reported position solution, the Talker ID is GN and the errors pertain to the combined solution.
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Old 02-05-2019, 10:33   #6
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Re: opencpn gps jumping

Have added two conditions to Jumping GPS with ais and no ais
https://opencpn.org/wiki/dokuwiki/do...aq#jumping_gps
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Old 02-05-2019, 10:35   #7
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Re: opencpn gps jumping

The Tab will not give solutions for the different constellations. It will blend the signals into one output.

That said the data stream with the individual xxGSV sentences etc. would be helpful to understand the issue better.

Composite boat is fine, but if a big carbon boom is sweeping forth and back you might get funny signals. Or any other electric or electronic device littering the frequencies the GPS is using.

Hubert
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Old 03-05-2019, 04:28   #8
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Re: opencpn gps jumping

I could reproduce it on land this morning. I saved a screenshot where you see the data NMEA data flow.
Is it easy to capture and register NMEA data?
Any comments?
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Old 03-05-2019, 05:28   #9
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Re: opencpn gps jumping

roede..
The GSV messages from different GNSS system are info about satellites and stuff like that. No positions.
The OCRMC contains the position and the "not usual" talker ID "OC" is probably indicating the gadget is creating the position from several sources? Check if more xxRMC are seen in the data stream? You can filter what's viewed in the NMEA debug window. Type for example "RMC" in the filter text field.
If you inbound GNSS unit is sending bad data in that way there is not much to do in OCPN. Check the options for your tablet if you can choose what GNSS system GPS, GLONASS etc.to use.
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Old 03-05-2019, 05:32   #10
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Re: opencpn gps jumping

Use the Connections filter to filter out all but one of those signals.

Then by changing the filter determine which sentence is the problem.


https://opencpn.org/wiki/dokuwiki/do...ections_window


Let us know what you find out.


PS: Hakan beat me to the response, his is good info too.
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Old 03-05-2019, 05:48   #11
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Re: opencpn gps jumping

Normally Samsung Galaxy equipment has had a full GPS included in the sensors.
I can find that in the specs! I've looked at several specs for the Tab S4 .

https://www.gsmarena.com/samsung_gal..._10_5-9262.php


I did find one item Key Features GPS Navigation, but no mention of the sensor itself

In the manual under location:
From Settings, tap Connections> Location. 2. Tap On/Offto turn on Location services. 3.Tap Locatingmethodto select how your location is determined: Highaccuracy: Uses GPS, Wi-Fi, and mobile networks

Please advise re the specs. OP wrote in first post:


Quote:
I am using the internal GPS of the tablet exclusively (no AIS data coming in either). It has GPS GPS + GLONASS, BEIDOU, GALILEO (from tech documentation). My doubt now would be that one of the systems is not working well in the west of France (Beidou?). But how could I filter out these?
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Old 03-05-2019, 09:24   #12
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Re: opencpn gps jumping

roede....


I notice from the screenshots that the GPS status indicator (upper right corner of screenshot) does not show full three bars. Usually this is an indication of poor skyview of the GPS receiver.
Are you outside?


Dave
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Old 03-05-2019, 12:21   #13
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Re: opencpn gps jumping

Dave...

from above

Quote:
Thanks for you remark.
It was a composite boat. The roof should not have so much influence on the GPS signals. As long as I remember there were always three green bars on the GPS icon. And the conditions were not like bringing the tablet outside.
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Old 03-05-2019, 19:16   #14
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Re: opencpn gps jumping

And yet, in the screenshots, I see less than three full bars on the GPS signal indicator....
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Old 03-05-2019, 22:55   #15
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Re: opencpn gps jumping

Quote:
Originally Posted by roede View Post
I could reproduce it on land this morning. I saved a screenshot where you see the data NMEA data flow.
Is it easy to capture and register NMEA data?
Any comments?
Capturing is very simple: just use the VDR plug-in.

Touching the tablet or leaning over it to observe the screen might be sufficient to block some satellites or to cause multi-path signals.
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