another question, my GPS can apparently give depth alarms but needs some kind of adaptor has anybody managed to connect there GPSmap up to transducer?
I'd imagine you need a depth finder putting out NMEA protocol with depth info on the interface.
spot on the manual says depth requires nmea input, but says little about what that actually is, guess its google time.
NMEA is a standard way of marine electronic devices to talk to one another over a serial interface. The information looks something like this-
Format of the depth sentence looks like this-
1) X1 = Depth, feet
2) f = feet
3) x2 = Depth, meters
4) M = meters
5) X4 = Depth, Fathoms
6) F = Fathoms
7) hh = Checksum
All way too much information really but it shows how these devices talk. You "should" be able to just hook things up and configure them to work.
Of course having interface cables running about can get messy and asking for salt water ingress. I'd have thought a depth sounder is going to have a depth alarm anyway so there'd be no need to send depth info to the GPS unless you want to log it.