I can see myself on new AIS transponder?

[Marco Flamingo]

I seem to have temporarily solved my Garmin MFD not picking up my GPS position by installing a Vesper AIS transponder connected with NMEA 2000. the Vesper instantly picks up satellites. I'll work out why the Garmin internal GPS isn't receiving later.

What is kind of weird is that the Garmin "little boat" icon shows where I am, but behind me is my own AIS icon labeled CHITON. It's like I'm following myself. The icon is in red, meaning that it is a vessel with which I might collide. Is this normal? It was odd watching the MFD in 1/16th mile range where the CHITON AIS icon would freeze with the trajectory line pointed at me but be left in my wake for 30 seconds, then leap forward on to my stern. This can't be what everybody is putting up with.

Vesper has a usb connection, but I haven't explored it with my laptop. Maybe this is how I turn off the menacing ghost CHITON?

 

[jimdavi]

My Garmin system7600xsv, does not show my AIS.

 

[ScottRhodes13]

No it's not normal to see yourself as an AIS icon. But since you do, the freezing, then jumping ahead would be normal, as a class B transponder only transmits position via VHF every 30 seconds.

Do you have another AIS receiver, using a different antenna, that might be receiving the transmission from your transponder?

 

[O C Diver]

As others have eluded to, your Garmin is working correctly. The icon in the center of your screen is your boat but doesn't show as an AIS target, as that has no value to you. To verify that your Garmin is transmitting an AIS signal (if you have a properly setup AIS transmitter) go to Marinetraffic.com and if in an area with one of their receivers, you will eventually see your boat. Remember that there is often a lag time before Marinetraffic.com displays your boat. They have a very good app that I use to verify my transmitter and see where my friends are.

Also, you most definitely don't want to transmitt two AIS signals. As the position only updates every 30 seconds, it would be easy and dangerous to confuse another boater into thinking you're two boats, especially in limited visibility (night, fog, and rain storm).

Ted

 

[twistedtree]

With AIS there is the notion of "own ship", i.e. your own AIS transmission. For displays to filter it out, they typically need to know your MMSI number. I think in N2K and/or 0183, the AIS device can tag "own ship" AIS reports, but I'm not certain about that.


This becomes a problem most often when a boat has both an AIS transceiver, and some form of AIS receive-only device. The receive-only devices are often unaware of your MMSI, so when your transceiver sends a report, the receive-only device hears it just like any other target, not knowing it's actually you.

 

[Marco Flamingo]

This becomes a problem most often when a boat has both an AIS transceiver, and some form of AIS receive-only device. The receive-only devices are often unaware of your MMSI, so when your transceiver sends a report, the receive-only device hears it just like any other target, not knowing it's actually you.

That might be where the problem lies. Prior to installing the Vesper transceiver, I was using the AIS receive-only capability of my radio (SH GX2400) to see AIS targets on my Garmin MFD. But I could not get the Garmin to reliably locate satellites and produce a GPS location. So the AIS targets would show up, but sometimes relative to an old inaccurate position. I could not get the Garmin to also use the GPS position provided by the radio.

After installing the Vesper, I instantly got satellites, my location, surrounding AIS targets, and my own boat. But I assumed that the Vesper had taken over transmitting both GPS position and all AIS targets to the Garmin. Now I see that's probably not true. The Vesper is providing my GPS location, but the radio might still be providing my AIS targets and not recognize that CHiTON is me. Kind of odd as my MMSI is also programmed into the radio. And when I look at the radio screen I didn't see a CHiTON icon or in its AIS listing. Still, maybe there is a "don't recognize me" setting on the radio.

Back to the marina.

 

[DDW]

I have seen myself trailing myself, using a Vesper 8000 and no other receiver. This happens usually when in a deep canyon or with high bluffs close by. I think it is multipath interference or reflections, but haven't really debugged it beyond that. It would go away when in open water. That is on the sailboat with the AIS antenna mounted about 40' above the water on the mizzen mast. I've never seen it on the trawler (also with Vesper 8000), even in the same conditions and locations.

If you have two receivers operating, and both providing AIS sentences over NMEA, then that is more likely the problem.

 

[porman]

When I added an AIS transceiver I had to go into the settings on my VHF radio, which is also an AIS receiver, and turn off the AIS tracking.

 

[twistedtree]

That might be where the problem lies. Prior to installing the Vesper transceiver, I was using the AIS receive-only capability of my radio (SH GX2400) to see AIS targets on my Garmin MFD. But I could not get the Garmin to reliably locate satellites and produce a GPS location. So the AIS targets would show up, but sometimes relative to an old inaccurate position. I could not get the Garmin to also use the GPS position provided by the radio.

After installing the Vesper, I instantly got satellites, my location, surrounding AIS targets, and my own boat. But I assumed that the Vesper had taken over transmitting both GPS position and all AIS targets to the Garmin. Now I see that's probably not true. The Vesper is providing my GPS location, but the radio might still be providing my AIS targets and not recognize that CHiTON is me. Kind of odd as my MMSI is also programmed into the radio. And when I look at the radio screen I didn't see a CHiTON icon or in its AIS listing. Still, maybe there is a "don't recognize me" setting on the radio.

Back to the marina.

This touches on another loophole in the various standards which is that there is no stipulation of who does the filtering. Maybe it's the receiver, maybe it's the display, maybe it's both, and maybe it's neither.


Unless you disconnected or disabled the VHF's AIS receiver, you Garmin chart plotter is likely now receiving duplicate AIS reports, one from the VHF and one from the Vesper. This risks overloading the Garmin, so I'd somehow turn off the reports from the VHF. I have yet to see a VHF with a setting to disable AIS, so you will probably need to disconnect the 0183 feed from the VHF to the Garmin. Or alternately turn off the receiving port in the Garmin, assuming it's not also using the transmit half of the port. You might also be able to tell the Garmin which data source to use for AIS. That might actually be the best approach if it's supported in the Garmin. Tell it to use the AIS info on N2k, and not the info on the 0183 port that connected to the VHF.