[OpenSource_GPS] GPS-determination velocity with carrier phase

[tebinuma]

Hi Filipe,

How much is the time span between two consecutive
phase measurements and how do you get "observed"
range rate from them?

The GPS satellites are accelerating at <1G. That 
gives you a few m/s difference in range rate every
sec.
If you take an "average" range rate using two phase
measurements, i.e. [v(t+dt)+v(t)]/2, the "observed"
range rate is not instantaneous but in the middle of
the time span, dt, by assuming a constant acceleration
during that time. This might give you those small
offsets in your velocity estimates.

Hope this helps,

Tak

--- Filipe Santos <fbnsantos at gmail.com> wrote:

> Hello,
> 
> Sorry for my email, but I'm looking for help on GPS
> for determination 
> velocity...
> I'm working on GPS data, and I'm using the carrier
> phase for 
> determination of velocity, but in static test the
> results have a bias  
> (like offset -1m/s , 1.4m /s and 0.4 m/s) , what
> could be the problem? 
> can anyone help-me?
> 
> I use
> 
> obs = Hv
> 
> and H is the direction cossenos
> obs= derived( phase) - dtcorr*v_light + Hv_{velocity
> of satellite, given 
> by derivation of equations of ICD  }
> 
> were dtcorr is the derive clock drift = Eph(2,k)*dt
> + Eph(20,k)
> 
> and solve this by means of least squares..
> should I subtract something else? the relativist
> term should be used?
> 
> the ionosphere and troposphere could be neglected  ?
> 
> I have attached one graf witch the red is velocity
> derived by position 
> and blue is the estimation by using carrier
> phase....
> 
> many thanks,
> Filipe Santos
> > _______________________________________________
> opensource_gps mailing list
> opensource_gps at lists.psas.pdx.edu
>
http://lists.psas.pdx.edu/cgi-bin/mailman/listinfo/opensource_gps
> 


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