Derive ship midship position from multiple GPSs

[mgrouch]

In case of multiple GPS NMEA sources Signal K should maintain
location of the antenna for each
GPS source individually and
calculate midship GPS position
taking into account antennas location on the ship.
Otherwise speed and AIS, anchor watch can experience sudden jumps
in GPS readings from different antennas.
I think there should be a signal K plugin which would handle that by sending upstream NMEA sentences with the position adjusted to midship.
Thanks

[tkurki]

That's an interesting idea! The way to go about it would be to add positional metadata about each sensor / position source under /sources. The calculation itself is not very complex. The plugin should use https://github.com/SignalK/signalk-server-node/blob/master/SERVERPLUGINS.md#appregisterdeltainputhandler-delta-next-- to intercept incoming messages.

[mgrouch]

Is it possible to implement some kind of self calibration logic constantly adjusting so that the position output from signal K will be consistent relative to some fixed point on the ship? There is gotta be some kind of existing algorithm for that

[mgrouch]

GPS Distance From Bow, GPS Distance From Center in settings
doesn't make sense to me. Which GPS? There could be many
in different places on a ship

[tkurki]

The that AIS transmitter is using. Or put it the other way: this is where gps receiver position on the ship from class A ais messages goes.