Re: [gpsd-dev] [PATCH] Using GOODTIME_IS for UBX_MODE_TMONLY.

[Hal Murray]

address@hidden said:
> I looked into this possibility at one point and it turned out to be
> uninteresting; the non-T variants already deliver more precision that WAN
> time service can use, practically speaking, so the T variants would be
> overengineering.  They might be a good fit for PTP over a LAN. 

I'd expect the T variants to keep delivering accurate time with fewer 
satellites.

Starting from scratch, you have 4 unknowns: X, Y, Z, and T.  (or the polar 
equivalents)  So you need 4 satellites to give you 4 equations so you can 
solve things.

If you assume you are on the surface of the earth and you have a good model 
of the globe (or your part of it), then you can get away with only 3 
satellites.  If you know your position, you can get the time from only one 
satellite.


-- 
These are my opinions.  I hate spam.