New networked systems questions

[bobfnbw]

Hey all.
Currently I have a Ray ST60 system on board for depth, speed and wind.I also have a r70 radar, garmin gps (older model) and a hand held gps.
The wind instrument died, and I since I am planning in the future to change to a networked garmin chartplotter like the 4212, I wonder if it would be better to just go with that system, the garmin wind and sounder.
This would give gps, speed over ground, depth, wind. The only thing it wouldn't have that I know of is speed in water, as there is no speed transducer that I can see.
So the question is, why would I need this, instead of the speed via gps ?
I understand the gps might not work someday, but then raymarine instruments fail as well. Anyone have something like this on their boat ?
Bob

[Amgine]

It's usually useful to know what your speed through the water is as you can then determine your set and drift from the current. With the GPS you can determine your VMG (velocity made good) and COG (course over ground). By adding speed, set, and drift to the numbers you have available you can make better navigational decisions, such as course corrections, estimations of where you will be when, and the ever-important wth is the tidal current going to do to me in an hour/3 hours/6 hours/etc.

Of course, having this information is pretty useless if you don't know what it means or how to benefit from it. I try to make the frustrating drifting days into practice the navigation skills days, using all the information I can collect to determine where I am, where I'm going, how to get where I want to go, when I'll get there, etc. Sometimes it keeps me from firing up the iron genny; other times it tells me when I should fire it up. And I delude myself into thinking I'm becoming a better sailor by practicing.

[Beausoleil]

Bob,

The Garmin sounder module looks like it supports transducers which also have speed and water temp, just like my Raymarine DSM 300 digital sounder. Speed over water is a gotta-have, not just a nice-to-have...

[bobfnbw]

Originally Posted by Beausoleil

Bob,

The Garmin sounder module looks like it supports transducers which also have speed and water temp, just like my Raymarine DSM 300 digital sounder. Speed over water is a gotta-have, not just a nice-to-have...

Thanks. Yeah I see now that they have a transducer for it.
Would be nice to upgrade.
Bob