Re: [gpsd-users] SDDBT

[Hamish]

Eric wrote:
> git head now parses SDDBT and returns soundings as negative
> altitudes.

Hi,

is that to mean that the depth below sounder when present replaces
the GPS's "z" component of the xyz antenna position solution?
if so, please don't do it like that.

the gps antenna, transducer, and reflection off the sea floor
happen at three different positions in space, each with their
own u,v,w velocity components and accelerations. and so while
related, can't be mixed and matched directly. (not to mention
different datums & reference frames to take into account)
This math happens and (recklessly generalizing) is why the
Texas Instrument corp. came to be.


if you just mean the sign is reversed relative to the gps
elevation, then thanks, that's fine.


model number of the Furuno derived SBT data to follow once I get
back into the office.


thanks,
Hamish