Newbie mapping a river

According to the specs on your chartplotter, "external antennas supported via NMEA 0183 and NMEA 2000". So in theory you could connect a more accurate GPS with the right cable and NMEA output settings. I've actually thought about trying this for a poor mans hydro survey (only for mapping fishing spots of course!).

Here's the setup the other way around. X, y, z of the transducer via RTK, depth from the sounder back to the controller = seabed elevation.

Try these guys. I've bought from them and visited their store, although they don't sell much over the counter.

https://www.thegpsstore.com/

Mikemmm, post: 420457, member: 12605 wrote: hi I use my fishfinder gps to map a river. I use insight genesis aka go free software to do this. My gps has waas and I map at 5 to 10 mph. How can I dramatically improve my gps accuracy? My gps updates at 5 times per second. Would dgps help? If so where can I buy an antenna for mylowrance hds5 gen2?

Find any dealer that sells the hds5:
http://www.lowrance.com/en-US/Products/NMEA-2000/Point-1-en-us.aspx
This unit is a 10 hz unit, and looks like it should plug right into your unit. Here's the installation manual:
http://www.lowrance.com/Root/Lowrance-Documents/GPS-Compass_IG_EN_988-10439-002_w.pdf

Richard Imrie, post: 420468, member: 11256 wrote: Here's the setup the other way around. X, y, z of the transducer via RTK, depth from the sounder back to the controller = seabed elevation.

I did not think rtk was practical for boating. Can I use dgps?

RTK gets you centimeter accuracy on x, y, z of the transducer position but you need a base and rover (or network rover). I haven't heard of dgps for a long time.