Everyone has heard of radar. It has been in use since 1940. On our boat we have the Furuno DRS2D 19" UHD. Furuno has one of the best radomes on the market. It is excellent and provides a 24nm range. Radar is not just for avoiding collisions, but also viewing weather. The biggest drawback to using radar full time is it's power consumption. It's not easy on the juice. A key consideration for a sail powered vessel.
Enter AIS. "Automatic Identification System (AIS) is an automated tracking system used on ships and by Vessel Traffic Services (VTS) for identifying and locating vessels by electronically exchanging data with other nearby ships and VTS stations. AIS information supplements marine radar, which continues to be the primary method of collision avoidance for water transport. Information provided by AIS equipment, such as unique identification, position, course, and speed, can be displayed on a screen. AIS is intended to assist a vessel's watchstanding officers and allow maritime authorities to track and monitor vessel movements. AIS integrates a standardized VHF transceiver with a positioning system such as a LORAN-C or GPS receiver, with other electronic navigation sensors, such as a gyrocompass or rate of turn indicator." Source: Wikipedia
|Green triangles are AIS targets|
A transponder transmits your location, speed, heading, etc to other boats, a receiver only receives the transmission from others. Your ship is invisible without a transponder. This can be a good thing I suppose if you were sailing through pirate alley. I'll just power down if needed...
The only argument against getting a transponder is large shipping vessels don't always pay attention to smaller (Class B) vessels. This may be true in some respects. However, I would rather error on the side of sending out a signal vs. relying solely on a radar reflector.
|Vesper Marine 850|
Next question, 'which' AIS transponder to purchase? I did a lot of research, and decided on the Vesper Marine 850. They key reasons for this decision are outlined below:
- This is a low power (3 watts) stand alone unit
- Interfaces via NMEA 2000 to the Furuno chart plotters at helm
- Provides AIS & Anchor Watch visibility inside at nav station
- Similar cost to Furuno AIS transponder
- Exceptional anchor watch functionality
- Excellent target filtering
- Ability to mount external collision/anchor alarm in master suite
In conclusion, it was a no-brainer to go this direction. A lot more flexibility and functionality than using the Furuno AIS transponder, without additional costs.
|Nav station with Vesper Marine 850 on far left.|