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Old 16-12-2017, 05:29   #1
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Increasing the number of GPS channels reported

I've recently played with a new USB mouse GPS receiver that can pick up signals from
GPS, SBAS, GLONASS, BEIDOU, GALILEO and QZSS. Out of the possible 72 channels, 32 can be active at the same time.
See
Navilock Produkte 62523 Navilock NL-8002U USB 2.0 Multi GNSS Empfänger u-blox 8 1,5 m

Here is a random screen pic (u-center app https://www.u-blox.com/en/product/u-center-windows) showing 18 sat received with the mouse near a window in an urban canyon (G = GPS, R = GLONASS, E = Galileo, SBAS (= EGNOS) not active)
Now it seems that the dashboard cannot display all these channels: the skyview keeps jumping (see the next two pics).
The debugger also reports between 9 and 6 sats (last pic).
Although the issue is not crucial, I suggest that some improvement in the display could be made...
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Old 16-12-2017, 06:21   #2
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Re: Increasing the number of GPS channels reported

Can you perhaps publish the NMEA stream to see the report of the other GNSS but GPS.

OpenCPN actually does recognize just the GSV sentences IIRC.
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Old 16-12-2017, 06:45   #3
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Increasing the number of GPS channels reported

The extra satellites are from a different constellation. So it is a bigger issue than just counting satellites. A couple extra satellites from a different constellation may not actually be improving the fix.

I have a question. Why does it matter how many satellites there are once you have 8-10?
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Old 16-12-2017, 06:57   #4
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Re: Increasing the number of GPS channels reported

Because the GNSS module will just pick the 4-6 best signals to calculate. The more choices you have, the easier to get a stable result.

What will be very interesting are the upcoming two frequency chips like the one from Broadcom which will hit the road early next near.
Especially for locations with difficult reception conditions. The Galileo L5 frequency shall help here quite a bit.

The two frequency receiver would allow to get centimeter precision using real-time corrections for example via LTE.
But not clear if the consumer devices will go that far. You need a very decent antenna as well.
Autonomous vehicles would love to get this precision, but in city canyons or tunnels this is still a long way.
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Old 16-12-2017, 07:01   #5
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Re: Increasing the number of GPS channels reported

Quote:
Originally Posted by bcn View Post
Can you perhaps publish the NMEA stream to see the report of the other GNSS but GPS.

OpenCPN actually does recognize just the GSV sentences IIRC.
Hi bcn
The GSV sentence is split between GAGSV pour Galileo, GLGSV for Glonass and GPGSV for GPS

Here is what e.g. GAGSV (Galileo) contains
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Old 16-12-2017, 07:02   #6
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Re: Increasing the number of GPS channels reported

With more than 6 satellites the extra ones are pretty much superfluous. So what good is there in knowing there are 42 satellites in view?
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Old 16-12-2017, 07:10   #7
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Re: Increasing the number of GPS channels reported

We don't know which ones the receiver is using for calculation.
And when you just show the GPS sats (being perhaps at low elevation) you might think the reception is bad as you don't see the 5 GLONASS and 4 GALILEOs that are giving a quality solution.

For me the sky view is nice picture, but more important would be the precision error estimate from the GNSS chip.
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Old 16-12-2017, 07:19   #8
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Re: Increasing the number of GPS channels reported

Bonjour SailorF54
Quote:
Originally Posted by sailorF54 View Post
I've recently played with a new USB mouse GPS receiver that can pick up signals from
GPS, SBAS, GLONASS, BEIDOU, GALILEO and QZSS. Out of the possible 72 channels, 32 can be active at the same time.
.....
Heureux de te lire.

Gilletarom.
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Old 16-12-2017, 07:25   #9
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Re: Increasing the number of GPS channels reported

Quote:
Originally Posted by bcn View Post
We don't know which ones the receiver is using for calculation.
And when you just show the GPS sats (being perhaps at low elevation) you might think the reception is bad as you don't see the 5 GLONASS and 4 GALILEOs that are giving a quality solution.

For me the sky view is nice picture, but more important would be the precision error estimate from the GNSS chip.
Here are the statistics on xDOP
PS I was under the impression that the higher the number of sats was, the lower HDOP was
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Old 16-12-2017, 07:46   #10
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Re: Increasing the number of GPS channels reported

From description of the uBlox chip:

Quote:
u‑blox M8 FW 3.01 now also supports Galileo, in addition to GPS, GLONASS, BeiDou, QZSS and SBAS. It can track up to three constellations concurrently and makes use of all SBAS and QZSS augmentation systems at the same time.
I would enable EGNOS

Quote:
Here are the statistics on xDOP
PS I was under the impression that the higher the number of sats was, the lower HDOP was.
This would be logical as the receiver can pick the optimal constellation.
the xDOP values are indicating the influence of the sat constellation geometry for the calculated solution.
< 1 optimal, >10 bad
More here:
https://en.wikipedia.org/wiki/Diluti...on_(navigation)
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Old 16-12-2017, 08:16   #11
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Re: Increasing the number of GPS channels reported

Quote:
Originally Posted by bcn View Post
...
I would enable EGNOS

...
I do agree (but I haven't go the view south that is required to pick up S120 / S136) (see pic)
One little snag: Using Franson GPSGate to open virtual ports seems to prevent WAAS/EGNOS reception
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Old 16-12-2017, 08:22   #12
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Re: Increasing the number of GPS channels reported

Quote:
One little snag: Using Franson GPSGate to open virtual ports seems to prevent WAAS/EGNOS reception
How should this be possible? WAAS/EGNOS is a function of the GNSS module.
Once enabled, it shall work with independence what the listening PC is doing.
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