HI, Sorry if this request has been raised, but I could't find it.
Could we have a second nmea feed from a second GPS?
I imaging a setup with 2 com ports configured to 2 nmea inputs, There then would be an input for antenna height for GPS 1 and GPS 2, then a GPS phase cenre separation distance. So GPS 1 being west and GPS2 being east ( or north south).
Then the live feed would have heading from the the positions of the 2 GPS units, both moving and stationary.

I have a low cost RTK setup which i'd like to use this for. RTK 2cm positioning for under $2000.

Thanks a bunch

Andrew

It's a nice idea, and we have experimented in the past with something similar - deriving headings from a pair of low cost (L1) RTK units, with surprisingly good results - see this post for more.
Actually combining two separate positions on-the-fly to calculate headings would, I suspect, be a rather niche requirement so I am not sure it would be a top priority for us. Better perhaps to log the raw data and post-process, before importing into RM? We have synchronisation of independently logged GPS data with sonar files as an upcoming feature later this year, which can really improve sidescan mosaic positioning.