New GPS issues - does the boat needs to move to in order to get the first fix?

[thomm225]

Originally Posted by sgel

Thanks again everyone for your suggestions and insights!
Since some people asked, ill clarify some points:
1) There is no internal GPS,
2) I am talking about the actual position and NOT on the COG/SOG
3) I called both Garmin and Simrad support, (btw I choose the gs25 since it have an internal direction sensor, compare to the Garmin 19x, and the direction sensor do work).
4) I took apart the nmea2000 network and remove all unnecessary devices.
5) I cannot move the boat since it on the hard, and once ill be in the water Ill have less time to investigate before Ill need to move her, I tried to move the antenna with no affect, but ill try to do it again.
6) I tired to search for preferred source configuration in the plotter or any configuration but couldn't find anything useful (there is no setup for position) ill try to search again. perhaps the nmea 0183 bridge configuration on the plotter causing some conflict, maybe I need to disable the gps pgn on that interface (all the wires are disconnected anyway)

Last update:
I called Garmin again , different guy, he confirmed it is weird and gave me some instructions how to get the debug information such as the pgn from the network and save it to the SD card(cool ) Ill do it later this week and send it to him.

Once ill get some updates / results Ill come back and update the thread.
In the mean time, happy new year everyone and thanks again for your help!
Sgel

It's not about relocating the antenna, it's about motion constantly for a few seconds to a minute for the system to update.

A good example would be a handheld.

My hand held will not update on COG/SOG/BRG unless it's in motion but it will show the correct Lat/Long position as will my mounted VHF/GPS/AIS without the boat being moved

[hoolie]

Originally Posted by thomm225

It's not about relocating the antenna, it's about motion constantly for a few seconds to a minute for the system to update.

A good example would be a handheld.

My hand held will not update on COG/SOG/BRG unless it's in motion but it will show the correct Lat/Long position as will my mounted VHF/GPS/AIS without the boat being moved

I'm not sure of the point you're making? The OP has said - unlike your own experience - he does not get Lat/Long transferred from his GPS when stationary. As others have pointed out it's undoubtedly a problem of incompatible N2K PGN data, an issue your handheld clearly doesn't have.

[CarinaPDX]

Originally Posted by s/v Jedi

The ignorance and confusion in this thread is disturbing

No kidding.

Let's go back and think this through:

1) We know the GPS is working (at some level) because the chartplotter reports receiving the device's announcement PGN. We also know that it is receiving the satellite status PGN (one per sattelite). Since the satellites' status are in the green we know that the GPS unit has everything in needs to calculate the position. IMHO there is near-zero chance that the GPS is not putting out the position, and quick position, PGNs.

2) We know that the N2K network is working because the chartplotter is reporting receiving the announcement and status PGNs from the GPS. It is not a network problem.

3) We know that both the GPS and chartplotter use the same PGNs (see my post #33) so there is no confusion there - or shouldn't be if paying attention.

4) As was noted way back near the beginning of the thread, the problem appears to be that the chartplotter is not using the Simrad GPS as the source of position data - and that continues to be the case. This chartplotter does have a screen that is used to select data sources (Configure/Communications/Preferred Sources). This seems to be an obvious place to start: OP (sgel) can you please take a photo of that screen and post it? While you are at it please post a photo of the Device List under Configure/Communications/NMEA 2000 Setup, and any other relevant screen. On my chartplotter there is a setup screen for each networked device that allows selection of which PGNs to process from that device - does this chartplotter have something similar under the NMEA 2000 Setup?

Unfortunately Garmin is one of the suppliers that thinks it is more important to keep things simple for its challenged customers than to provide them with easy access to important information, both on the chartplotter and in the manual. Without a better manual I can't tell what those screens look like. And without a log of the PGNs received it is difficult to troubleshoot to say the least. I am so grateful that I decided to pay more and get a professional grade chartplotter from Furuno; the manual is encyclopedic and the firmware has more features than I could ever use, including for setup and troubleshooting. Just sayin'.

Greg

[thomm225]

Originally Posted by hoolie

I'm not sure of the point you're making? The OP has said - unlike your own experience - he does not get Lat/Long transferred from his GPS when stationary. As others have pointed out it's undoubtedly a problem of incompatible N2K PGN data, an issue your handheld clearly doesn't have.

It's always a miss in communication on here I think.

I was responding to his posting of this:

5) I cannot move the boat since it on the hard, and once ill be in the water Ill have less time to investigate before Ill need to move her, I tried to move the antenna with no affect, but ill try to do it again.

It's not about moving the antenna when we are talking SOG, COG, or BRG.

Hopefully now you understand why I mentioned my handheld

Earlier I missed the fact that his boat was on the hard and he couldn't easily move it.

So now it's either he hooked it up wrong or configured it wrong.

This after seeing random posts.

[continuouswave]

Originally Posted by Dr. D

Actually, even 5 mph is a lot. GPS receivers use both pseudo-range and Doppler shift to calculate position and speed. The use of Doppler shift for speed can be even more accurate than using two fixes and time.

The speed of motion of the GPS receiver at 5-MPH won’t affect the position solution accuracy. The claim was not about speed measurement but that motion of the GPS receiver was necessary to just get a position solution.

Please cite a marine GPS receiver that uses Doppler shift to measure speed.

I am aware that some specialized-use GPS receivers can measure the speed of their motion with Doppler shift, but I don’t recall any particular common marine GPS that does this. If you could mention the ones that do, to learn of them will be interesting.

[Dockhead]

Originally Posted by Dsanduril

Take a look in the 5212 at the "preferred sources" (and maybe the "speed sources") configuration items. There may be a setting there that is telling the Garmin gear to use the old 0183 data. IIRC (but from memory, so may need to consult a manual):
Configure->Communications and
Configure->Preferences->Navigation

It's a long shot, but the only thing I can think of that would have the Garmin ignore the new data.

[Edit] I agree that there should be no reason you need to move to get a GPS fix, but if it's not too much trouble with the cabling, you can always "move the boat" by moving the antenna.[/Edit]

That's not a "long shot", that is almost certainly the problem.


Your NMEA2000 network will not necessarily find and recognize a new data source automatically. I don't know how this works on Gamin, but with Navico stuff this will certainly not happen. With Navico stuff you can initiate an automatic search for data sources or you can manually set the network to recognize this device as source of position, time, etc. data.


On Navico, you go look first at the device list and find the instance number of the new GPS. Then you go to "sources" and set that device as the source for the various types of data you want to get from it.


If you don't do this, most likely the network will not know where to take this data from and will show it as missing. NMEA2000 networks are very different in this respect, from 0183 ones, and it's actually one of the advantages -- you can have multiple sources of the same data on the same network, and you have the means to choose which source you want the network to use. I think you can even have different devices choosing different sources of the very same data.

[sgel]

Hi Everyone

I went back to the boat and made some additional tests. (all with only the GPS, plotter and power connected to the network)
I search the configuration again and there is no Configure/Communications/Preferred Sources anywhere (and not under navigation). I went over all the menus over and over
On the plotter side I disabled everything related to the nmea 0183 network, bridge , all the pgn types etc..

Using the instruction I got from Garmin, I recorded the traffic on my nmea 2000 network and I can see that the Simrad GPS is working and is transmitting the right PGNS.

Eventually I got some longer wire and connected it to antenna and moved it fast around, the position did update on the plotter, but once I stopped moving it stopped updating again. (the question mark appeared again on the boat image).

Please find some photos below.

I sent all the logs and the screenshots to Garmin and I am waiting for their reply. I don't think there are any action we can do right now beside waiting for their reply.

Thanks again everyone for this very insightful discussion.
Sgel

[s/v Jedi]

Is this the only nmea2000 display you have? Do you have a multifunction display that can show position, date, time, cog and sog? This plotter doesn’t decode the fields so it’s hard to read, but I could not find the hex code from the fast position update in the gnss position message?

[sgel]

Originally Posted by s/v Jedi

Is this the only nmea2000 display you have? Do you have a multifunction display that can show position, date, time, cog and sog? This plotter doesn’t decode the fields so it’s hard to read, but I could not find the hex code from the fast position update in the gnss position message?

I disconnected the multifunction display when I preformed the tests.
Do you mean this hex code-
Sequence # Timestamp PGN Name Manufacturer Remote Address Local Address Priority Single Frame Size Packet

18 501630 129029 GNSS Position Data Simrad 127 255 3 0 43 0x005A472045382B006C3E41DC69A90600B432A266DB09EF70 89EDFFFFFFFFFF12FC003C0064005CF9FFFF00

[CarinaPDX]

The "Preferred Sources" setup page was referenced in the manual I found online. If it is no longer there, there must be some other (perhaps automatic) means of selecting sources and again, that seems to be the source of the problem. If the source decision is automatic then perhaps it is getting tripped up by one device having two functions (GPS, compass). What happens when you select the Simrad "antenna" and then "review" in the Device List menu?

Considering that the inadequate manual available online clearly doesn't reflect your firmware this is going to be one for Garmin support to sort out. Good luck.

Greg

[mhsprang]

Sgel,

The contents of PGN 129029 clearly show you have a valid fix.

Your new GPS however uses Pinning, a feature where a stationary GPS outputs fixed and stable values for LAT, LON, an SOG set to 0.0 and a COG marked as "invalid".

You can see that in the screen shot of the PGN contents you posted. Look at PGN 129026 (COG & SOG): the COG field (bytes 3 and 4)contain "FFFF" which is a special NMEA 2000 value indicating "data not available". Your plotter therefore displays a "?" because it cannot determine the direction of the boat icon.

Best,
Meindert, ShipModul

[s/v Jedi]

Originally Posted by mhsprang

Sgel,
I analyzed the dump of PGN 129029 you posted and it shows a correct fix, taken at 1/5/2020, 20:08:30.8 UTC, Lat: 48º 00.18738', Lon: 122º 13.22754', Type of system: GPS + GLONASS, Method: GNSS Fix. The remaining values also make sense, except the number of satellites visible: the PGN reports 0.


But your earlier message got me thinking: you said when you moved the antenna, "you got a fix" and when you stopped moving the antenna "it stopped updating again. (the question mark appeared again on the boat image)". The following is happening in your case: your new GPS uses Pinning, a feature where a stationary GPS outputs no COG because it is not moving. You can see that in the screen shot you posted: bytes 3 and 4 of the dump of PGN 129026 contain "FFFF" which means "data not available". You plotter therefore displays the "?" and confusion is imminent.Conclusion: you do have a valid fix!


Best,
Meindert, ShipModul

Thanks for decoding the data Nice to have a professional aboard

With a valid position on the network, displays showing position should just display that lat and lon and only cog and sog should show up empty.

[tanglewood]

So much for compatible use of the same PGN

[mhsprang]

Originally Posted by tanglewood

So much for compatible use of the same PGN

How is that? Since the inception of NMEA 2000 it is allowed to mark fields to "not available" if the information/value of that field is not available. In this particular case the implementor of the firmware in that plotter has chosen to show a question mark if a GPS has no COG and possibly failed to mention that in the manual. Or maybe the OP hasn't read the manual
After all, we are men and we don't read manuals. Yet we complain that our wives didn't come with a manual, right?

Meindert, ShipModul

[Dr. D]

Originally Posted by continuouswave

The speed of motion of the GPS receiver at 5-MPH won’t affect the position solution accuracy. The claim was not about speed measurement but that motion of the GPS receiver was necessary to just get a position solution.

Please cite a marine GPS receiver that uses Doppler shift to measure speed.

I am aware that some specialized-use GPS receivers can measure the speed of their motion with Doppler shift, but I don’t recall any particular common marine GPS that does this. If you could mention the ones that do, to learn of them will be interesting.

Please read section 1107 in:
https://en.wikisource.org/wiki/The_A...ioning_Service


I do not believe (I may be wrong) that any of the marine GPS receiver manufacturers make their own GPS chipsets. Instead they buy them from SiRF (https://en.wikipedia.org/wiki/SiRF) and other manufacturers. Those are the guys using the Doppler information.


So, you are correct I can not state which marine GPS receiver uses Doppler, but I think most chipset manufacturers do so.


(My apologies for going down a rabbit hole; this doesn't help the OP.)