May 15, 2006

AIS Update - Nobeltec's AIS 100 Receiver with VNS 8.1.2000

I thought you might be interested in our experiences so far with Nobeltec's Visual Navigation Suite 8.1.2000 (the latest patch level) and their Single Channel AIS 100 Receiver.

Installation was pretty easy - running the cable to our antenna arch was fun of course. The 4' Shakespeare VHF Antenna we're using is now occupying the last of our 6 mounts. Hmmm - this confirms that I'm a technoid geek if I've used all 6 mounts (2 GPSs, a CARD, Iridium antenna and Sirius Satellite Radio antenna take up the other 5 mounts).

Connections to the unit were 12V, the VHF Antenna and a serial port to the computer. Fortunately I have a permanently installed USB hub with unused ports and an extra serial to USB adapter on board. The Serial Port on the AIS 100 outputs NMEA-0183 formatted sentences at 38.5 kbps, so we really could not multiplex into our 4.8 kbps NMEA multiplexer system.

Firing everything up - It worked out of the box. See http://raptordance.com/VNS-AIS-Display.jpg for a screen shot.

We're up in Gibson's Landing, across Howe Sound from Vancouver today and I've counted 34 targets that I'm tracking. It's really interesting as you have a lot of information about many of the vessels - e.g. destination, cargo, etc.

Overall, the system works OK.... Mostly....

VNS 8.1.2000 Crashes a lot - it seems to suffer from memory problems and freezes up every few hours and requires restarting. So far Nobeltec support hasn't answered my emails. I'll try calling them later (you really don't want to try to reach them on Monday mornings). I've already followed some of their advice to no avail.

The basic problem with this current set up is that VNS and the AIS 100 don't show all the targets! Also, targets that should remain visible disappear from time to time. The disappearing targets are often closer to us than other targets that remain and often within physical line of site. So, I don't think it's a problem with VHF reception. Some of the disappearing targets are quite close and a possible collision hazard. My theory is that this is due to the fact that the AIS 100 is a single channel receiver, the disappearing target ships' transponders have switched to the other AIS Channel. To try to continue displaying these targets, I have raised the AIS/ARPA Timeout value in VNS to 600 seconds (10 minutes). This didn't seem to noticeably change behavior.

If you have other thoughts about what might be going on, drop me a note!

I'm thinking that single channel AIS receivers may be of much less value than believed (I played with using the worthless word, but I'm still think it has some value). We'll most certainly upgrade to a 2 channel receiver when prices come down.
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