We have both and I have to say that whereas Furuno's ARPA is better than nothing but it is problematic in high seas. In calm weather it is flawless. However, in big seas it can lose the target and acquire a wave and then transition back to the target unless quite far away in which case it will simply adopt a wave and follow it or sometimes jump from wave to wave. Also, we need to change the "vector time" setting in order to prevent falseing in big waves from giving us wild variations in heading. Unless set for a relatively long time, a vector time setting you'd use in calm conditions for a fast target is far too short for a slow boat at five miles in big seas. OTOH, AIS has proven dead on, and when there's a difference vis-a-vis ARPA we know which to trust! Regards, John "Seahorse" >Thinking about Johns questions, a few weeks ago I was traveling with another skipper who had invested in Furuno's fantastic AIS system, but had passed on adding the ARPA card to his chartplotter/radar. While I'm a fan of AIS I think an ARPA feature is much more valuable and would be the first thing I'd buy (or recommend). I have used ARPA hundreds of times and the Furuno implementation is fantastic. I was really surprised how good it was compared to the Nobeltec solution I had on my Camano. The nobeltec software seemed to be running the course analysis algorithm too fast, resulting in wildly changing course vectors. It may also have been that they didn't average the selected target very well, accounting for the wild course output. Anyway the point is while AIS is great, I think ARPA is a requirement for passagemaking, while AIS is a "really nice to have". Scott Bulger, Alanui, N40II, Seattle WA **************Play online games for FREE at Games.com! All of your favorites, no registration required and great graphics b check it out! (http://pr.atwola.com/promoclk/100000075x1211202682x1200689022/aol?redir= http://www.games.com?ncid=emlcntusgame00000001)

John shared: We have both and I have to say that whereas Furuno's ARPA is better than nothing but it is problematic in high seas. & OTOH, AIS has proven dead on, and when there's a difference vis-a-vis ARPA we know which to trust! Scott replies: Interesting, your describing behavior Ibve not observed on my Furuno system. I had a Navnet1 6kw model 1943 unit which I then upgraded to Navnet II. Both systems worked great. However we never really saw any big seas. 10 foot was about average with the occasional 15, but 95% of the time few if any whitecaps, which is what Ibd assume the radar would pick up. As far as what to trust, well if you consider the technology involved using AIS delegates some trust to the other guy, that his unit is reporting correctly, A fairly safe assumption. On the other hand RADAR is 100% on your unit, under your control. Considering the number of boats without AIS Ibd sure feel better about trusting my RADAR than someone elsebs AIS transmitter. Scott Bulger, Alanui, N40II, Seattle WA Leaving Annapolis for Solomons MD this morning