SOG and COG ?

[petit bateau]

I wonder if anyone can help re SOG and COG and how it is generated on OCPN, and why it might not be displayed for me in a Windows-OCPN.

I run two OCPN systems:

1. Android tablet, not networked, purely standalone and with WiFi switched off, using its own internal GPS. This correctly shows a SOG and COG in OCPN in the lower left/centre of the screen ribbon. (It also shows ship position absolutely fine).

2. A Windows PC, connected to a SeatalkNG network via a gateway, and sourcing its position from the network. The ship's position, and tracks show up absolutely fine and are correct. However it is not showing SOG and COG on the OCPN and never has. Why might this be ? What should I do to correct this ?

Here is an old image of the Windows-OCPN screen. As you can see the SOG and COG just show --- .



(In the example screenshot the red bubbles are highlighting some false ship tracks/positions. That was caused at the time by a conflict between the Android GPS and the real GPS which at the time was both coming through onto the network. By removing the Android tablet from the network completely I have solved that, and since neither device sees any false data of this nature. But the missing SOG/COG issue is still vexing me.)

[Viking Sailor]

You have no GPS. Thus, no SOG or COG.

[ChrisJHC]

Originally Posted by Viking Sailor

You have no GPS. Thus, no SOG or COG.

To add a bit more to this (correct) answer: if you look in the top right hand side of the screen you can see red “ball”. This is the GPS indicator and turns green when you have an active GPS input.

[petit bateau]

Originally Posted by ChrisJHC

To add a bit more to this (correct) answer: if you look in the top right hand side of the screen you can see red “ball”. This is the GPS indicator and turns green when you have an active GPS input.

Thank you both for an answer, however I don't think it is as simple as that.

I do have a GPS on the network, that is where the position is coming from, see the lower left corner of the screen. It is also where the position is coming from for all the track info. The same position info is presented in the stng instruments. The source for the position info is the GPS in the combined VHF - AIS - GPS.

So why is ocpn not interpreting this as I would expect ?

[nohal]

It is as simple as that. If your data feed does not contain COG and SOG, it is not displayed.
Your data feed also does not seem to contain information about the quality of GPS signal and sats in view, that is why the GPS status indicator stays red.

[petit bateau]

Originally Posted by nohal

It is as simple as that. If your data feed does not contain COG and SOG, it is not displayed.
Your data feed also does not seem to contain information about the quality of GPS signal and sats in view, that is why the GPS status indicator stays red.

I'm sorry but I have inadvertently confused things by using an old screenshot that I took to illustrate a problem with a conflict between two GPS data feeds, that was intermittently resulting in erroneous positions, and hence tracks. I solved that by making the Android OPCN absolutely stand-alone, so that now only the Windows-OPCN has access to the STng system position information.

My apologies to @nohal @ChrisJHC @Viking_Sailor for creating any confusion.

So I have gone back to the boat this afternoon and taken the following image of the current Windows-OPCN screen. As you can see the GPS icon is in fact green. Yet still - and ever since the beginning of using Windows-OCPN - there is no SOG and no COG.

It is because there is in fact a GPS feed to the STng network that OCPN has been able to deduce the position and hence the track data you see in the screenshots. But still no SOG and COG.

I would be grateful for any suggestions, and any requests for further information. Once again my apologies for initially giving you all a confusing screenshot that led to an easy answer of 'no GPS' when I think it is not quite as easy as that. Hence my asking for help.



Normally I get a 3-bar GPS signal, but the system was still acquiring a full lock when I took the screenshot, hence only a two bar green at that moment.

[bcn]

From Options|Connections please enable the NMEA Debug Window and post some content here....

[petit bateau]

<GREEN>16:37:15 (TCP:192.168.4.1:60001) $HCHDM,27.8,M*14<0x0D><0x0A>
<GREEN>16:37:15 (TCP:192.168.4.1:60001) $WIMWV,303.44,R,3.6,N,A*16<0x0D><0x0A>
<GREEN>16:37:15 (TCP:192.168.4.1:60001) $GPRMC,153714,A,3855.2918,N,02053.0230,E,,,290924, 0,E,A,V*72<0x0D><0x0A>
<GREEN>16:37:15 (TCP:192.168.4.1:60001) $TIROT,2.79,A*07<0x0D><0x0A>
<GREEN>16:37:15 (TCP:192.168.4.1:60001) $WIVWR,56.6,L,3.6,N,1.9,M,6.7,K*70<0x0D><0x0A>
<GREEN>16:37:15 (TCP:192.168.4.1:60001) $SDDPT,2.24,0,*51<0x0D><0x0A>
<GREEN>16:37:15 (TCP:192.168.4.1:60001) $GPGGA,153714,3855.2918,N,02053.0230,E,1,10,2.53,0 ,M,0,M,,*4E<0x0D><0x0A>
<GREEN>16:37:15 (TCP:192.168.4.1:60001) $GPGLL,3855.2918,N,02053.0230,E,153714,A,A*4E<0x0D ><0x0A>
<GREEN>16:37:15 (TCP:192.168.4.1:60001) $GPGNS,153714,3855.2918,N,02053.0230,E,A,10,2.53,0 ,0,,,V*5F<0x0D><0x0A>
<GREEN>16:37:15 (TCP:192.168.4.1:60001) $IIMDA,,I,,B,,C,25.4,C,,,,C,,T,,M,,N,,M*07<0x0D><0 x0A>
<GREEN>16:37:15 (TCP:192.168.4.1:60001) $IIMTW,25.4,C*10<0x0D><0x0A>
<GREEN>16:37:15 (TCP:192.168.4.1:60001) $IIRSA,-31.2,A,,V*64<0x0D><0x0A>
<GREEN>16:37:15 (TCP:192.168.4.1:60001) $IIVHW,,T,27.8,M,0,N,0,K*46<0x0D><0x0A>
<GREEN>16:37:15 (TCP:192.168.4.1:60001) $HCHDG,27.8,,,0,E*0A<0x0D><0x0A>
<GREEN>16:37:15 (TCP:192.168.4.1:60001) $HCHDM,27.8,M*14<0x0D><0x0A>
<GREEN>16:37:15 (TCP:192.168.4.1:60001) $WIMWV,303.44,R,3.6,N,A*16<0x0D><0x0A>
<GREEN>16:37:15 (TCP:192.168.4.1:60001) $GPRMC,153714,A,3855.2918,N,02053.0230,E,,,290924, 0,E,A,V*72<0x0D><0x0A>
<GREEN>16:37:15 (TCP:192.168.4.1:60001) $TIROT,-2.45,A*25<0x0D><0x0A>
<GREEN>16:37:15 (TCP:192.168.4.1:60001) $WIVWR,56.6,L,3.6,N,1.9,M,6.7,K*70<0x0D><0x0A>
<GREEN>16:37:15 (TCP:192.168.4.1:60001) $GPGGA,153714,3855.2918,N,02053.0230,E,1,10,2.53,0 ,M,0,M,,*4E<0x0D><0x0A>
<GREEN>16:37:15 (TCP:192.168.4.1:60001) $GPGLL,3855.2918,N,02053.0230,E,153714,A,A*4E<0x0D ><0x0A>
<GREEN>16:37:15 (TCP:192.168.4.1:60001) $GPGNS,153714,3855.2918,N,02053.0230,E,A,10,2.53,0 ,0,,,V*5F<0x0D><0x0A>
<GREEN>16:37:15 (TCP:192.168.4.1:60001) $GPGSA,,,13,14,15,22,23,30,,,,,,,2.7,2.53,*5E<0x0D ><0x0A>
<GREEN>16:37:15 (TCP:192.168.4.1:60001) $IIMDA,,I,,B,,C,25.4,C,,,,C,,T,,M,,N,,M*07<0x0D><0 x0A>
<GREEN>16:37:15 (TCP:192.168.4.1:60001) $IIRSA,-31.2,A,,V*64<0x0D><0x0A>
<GREEN>16:37:15 (TCP:192.168.4.1:60001) $IIVHW,,T,27.8,M,0,N,0,K*46<0x0D><0x0A>
<GREEN>16:37:15 (TCP:192.168.4.1:60001) $HCHDG,27.8,,,0,E*0A<0x0D><0x0A>
<GREEN>16:37:15 (TCP:192.168.4.1:60001) $HCHDM,27.8,M*14<0x0D><0x0A>
<GREEN>16:37:15 (TCP:192.168.4.1:60001) $WIMWV,303.44,R,3.6,N,A*16<0x0D><0x0A>
<GREEN>16:37:15 (TCP:192.168.4.1:60001) $GPRMC,153714,A,3855.2918,N,02053.0230,E,,,290924, 0,E,A,V*72<0x0D><0x0A>
<GREEN>16:37:15 (TCP:192.168.4.1:60001) $IIVLW,1068,N,1068,N,,N,,N*4D<0x0D><0x0A>
<GREEN>16:37:15 (TCP:192.168.4.1:60001) $WIVWR,56.6,L,3.6,N,1.9,M,6.7,K*70<0x0D><0x0A>
<GREEN>16:37:15 (TCP:192.168.4.1:60001) $GPZDA,153714,29,09,2024,,*4B<0x0D><0x0A>
<GREEN>16:37:15 (TCP:192.168.4.1:60001) $TIROT,-7.44,A*21<0x0D><0x0A>
<GREEN>16:37:15 (TCP:192.168.4.1:60001) $GPGGA,153714,3855.2918,N,02053.0230,E,1,10,2.53,0 ,M,0,M,,*4E<0x0D><0x0A>

I'm at the dock going nowhere right now. Does this debug grab assist in diagnosis ?

[bcn]

Take your RMC message:
$GPRMC,153714,A,3855.2918,N,02053.0230,E,,,290924, 0,E,A,V*72<0x0D><0x0A>

which has the following structure:
$GPRMC,hhmmss.ss,A,llll.ll,a,yyyyy.yy,a,x.x,x.x,dd mmyy,x.x,a*hh
1 = UTC of position fix
2 = Data status (V=navigation receiver warning)
3 = Latitude of fix
4 = N or S
5 = Longitude of fix
6 = E or W
7 = Speed over ground in knots
8 = Track made good in degrees True
9 = UT date
10 = Magnetic variation degrees (Easterly var. subtracts from true course)
11 = E or W
12 = Checksum


and then the data for SOG and COG are empty...

[stevead]

GPRMC,153714,A,3855.2918,N,02053.0230,E,,,290924

There is no SOG or COG present in the RMC sentence.

Without seeing the underlying NMEA 2000 data it is impossible to ascertain whether your STng gateway or source of GPS data is at fault.

It is not a fault with OpenCPN. Perhaps revisit your gateway settings.

[petit bateau]

Originally Posted by bcn

Take your RMC message:
$GPRMC,153714,A,3855.2918,N,02053.0230,E,,,290924, 0,E,A,V*72<0x0D><0x0A>

which has the following structure:
$GPRMC,hhmmss.ss,A,llll.ll,a,yyyyy.yy,a,x.x,x.x,dd mmyy,x.x,a*hh
1 = UTC of position fix
2 = Data status (V=navigation receiver warning)
3 = Latitude of fix
4 = N or S
5 = Longitude of fix
6 = E or W
7 = Speed over ground in knots
8 = Track made good in degrees True
9 = UT date
10 = Magnetic variation degrees (Easterly var. subtracts from true course)
11 = E or W
12 = Checksum


and then the data for SOG and COG are empty...

Originally Posted by stevead

GPRMC,153714,A,3855.2918,N,02053.0230,E,,,290924

There is no SOG or COG present in the RMC sentence.

Without seeing the underlying NMEA 2000 data it is impossible to ascertain whether your STng gateway or source of GPS data is at fault.

It is not a fault with OpenCPN. Perhaps revisit your gateway settings.

Thank you both. And everyone.

That is why I phrased the question as being "I wonder if anyone can help re SOG and COG and how it is generated on OCPN, and why it might not be displayed for me in a Windows-OCPN." because I was unsure if OCPN was generating SOG/COG itself from the sequence of GPS positions, or whether it was generated in the GPS device.

If you recall this VHF/GPS/AIS is a Standard Horizon GX2400E. I have previously described some setup issues I found so as to help others - see post #20, #29, etc

https://www.cruisersforum.com/forums...-284800-2.html

I think it is about time I wrote to Yaesu and asked them a few questions. In the meantime I'll try putting a GPS puck on the WinPC. That's not really what I want to do as I'd rather all instruments existed on the NMEA2000 network rather than being PC-dependent.

In the meantime I'd hesitate to recommend one of these combined GPS-AIS-HF units.

(I'll let you know if I get an answer from Yaesu)

[petit bateau]

(I've now sent an email sent to Yaesu UK.)

[PippaB]

Sorry, not at my current installation, but my older one has an option to have OpenCPN calculate SOG/COG. Just don't know that it still exists.

I do know that it is not perfect as it tends to jump around depending on the precision of the position reports, but possibly useful to you.

[petit bateau]

Originally Posted by PippaB

Sorry, not at my current installation, but my older one has an option to have OpenCPN calculate SOG/COG. Just don't know that it still exists.

I do know that it is not perfect as it tends to jump around depending on the precision of the position reports, but possibly useful to you.


Attachment 294785

Thanks. It that just SOG/COG for AIS targets or also for one's own ship ?

(I've just checked and the dialog box still exists in 5.10.0-0)

[PippaB]

AFAIK it should be own ship only. SOG/COG of AIS targets is embedded in the AIS messages and comes from their data. Don’t see any AIS messages in your previously posted data sample, so can’t check for blanks/missing information.