Re: Check your GPS / AIS devices. Some of them failed on Jan 2, 2022 due to the "GPS Rollover" bug

David Crisp

With regards GP90 I can confirm Nick's message as I too have been in touch with Furuno UK about my GP90. 

FYI, I have a Furuno NavNet vx2 and RDP149, along with Raymarine AIS700 and Icom IC-M506 DSC radio, the AIS and DSC have their own internal GPS.  I'm not aboard at the moment but last season the Furuno vx2 displayed the track data from the AIS700 just fine.  I might try replacing the GP90 GPS data feed into the Furuno vx2 with the AIS GPS data output but I'm not confident it will work - from my VERY limited understanding I don't think the Raymarine AIS outputs the correct GPS sentence format.

If the Furuno technician is correct that the GP90 will provide good GPS position to the vx2 albeit incorrectly dated that's good enough for me and my modest explorations around Greece/Turkey.  I use the Furuno vx2 and chart plotter primarily to display AIS and radar data and as a backup to an iPad (with its own GPS) running Navionics.  Date stamping of tracks on the Furuno is not important to me.

In case it's of use here's the full text of the info' I got from Furuno:
"I think it best we start with the GP90, the GP90 should start working for outputting position data by carrying out the cold start procedure on the same article referenced. The date will be incorrect still but to my knowledge the position should still be correct and work as normal it just means things such as tracks will be recorded with incorrect date stamp, if the GP90 is feeding a DSC radio this could also cause issues as the incorrect date would be output in case of a distress alert.
I assume the VX2 unit already has the AIS interfaced so I presume the software is new enough to not require the interface, if you could confirm the VX2 software though it would enable me to have a better guess from my side. I have attached for your reference a picture of how to see what software version you have installed with the unit boots up and the software history of the VX2 unit which shows since V1.08 the need for a interface for a separate AIS interface was removed and handled in software on the VX2 itself. [I have attachments to this message]
Taking GPS data from a AIS into a unit as old the the VX2 is kind of unknown and certainly never tested with a competitors unit, please see possible set backs and you wont know until its been tested I am afraid:
BAUD rate - The AIS units normally speak at 38.4K BAUD and GPS is normally set to 4.8K BAUD, the VX2 may struggle to accept GPS data at this speed its never been tested.
Talker ID - NMEA0183 data has a talker ID stamp at the beginning so a typical GPS sentence structure is some thing like '$GPGLL,5051.7847,N,00118.7023,W,132236,V' and as you can see the beginning of the sentence starts with GP, the GP stands for GPS and denotes the source device. A typical AIS sentence looks like ' !AIVDM,1,1,,B,1CgWDt0000NGulhU?AAWv3;<0D1O,0*5A' so I am not sure the VX2 unit will decode GPS information in this format.
The GP320B was a very popular GPS to have fitted to the VX2 units and the sentences output on NMEA0183 were DTM/GGA/GLL/RMC/VTG/ZDA as per the attached document, if the Raymarine AIS can output these with a GP talker ID then this will be you best chance of getting it working assuming the VX2 can take GPS info from this device in mixed format at 38.4K BAUD. In the case of a Furuno AIS we have a proprietary data sentence which carries position data  over to the unit so we don't see the issue and have by design made our units compatible with each other."


Nick, looks like our boats are in the same place - I'm hauled out in Ionian Marine, hoping to get back late April.  Be great to meet up.

David Crisp
SV Wilna Grace
Amel 54 #58
Preveza, Greece

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