LEA-4T raw data extrapolation

Hi all,

i read few massages in sci.geo.satellite-nav about this problem, that
data from low-cost receiver need to be extrapolated before doing SD or
DD.

i also find few ways of doing it, by SamSvl and John

John:
EpochTime = NearestHz(ReceiverTime, 10);
Adjust = EpochTime - ReceiverTime;
for each satellite s
phase[s] += Adjust * (L1Frequency-doppler[s]);
pseudorange[s] += Adjust * (L1Frequency-doppler[s]) *
L1WaveLength;

SamSvl
1. corrected receiver time = receiver time + clock correction (from
position calculation)
for each sat
corrected pseudorange = pseudorange + clock
correction * c
corrected carrier = carrier + clock correction *
c / L1freq

at SamSvl algorithm, i dont understand the suggested carrier
correction eq., since c / L1freq = L1 wavelength, = 0.19m. in other
words, assuming clock correction is 1s, then the correction to the
carrier phase is only one cycle?? am i missing something?
concerning John idea, from the physical side, why do i need to
"correct" my doppler by computing
(L1Frequency-doppler[s])?
is the doppler it self repsent the rate of change of range?

I try to compute SD\DD base lines with LEA-4T receivers. Since the
LEA-4T receivers have clock's error of few ms, am i suppose to
extrapolate the rover data to:
corrected receiver time = receiver time + clock correction
or only the Rover to Base receiver time?

At John eq. he used doppler data to extrapolate the carrier phase
data, is the doppler data not too nosie for extrapolating phase data?
Regards

wrote:
pler[s]);
doppler[s]) *
rom
nge + clock
ock correction *
r

Hi Hannan,

The observations of one receiver have to be inter/ extrapolated to the
observation time of the other
receiver. I usually interpolate the reference data because my
reference is stationary and inter/
extrapolating stationary observations tends to be more accurate than
observations from a moving
receiver.
Before inter/ extrapolation both receiver clock errors need to be
removed from the receiver time and
observations. See e.g. the RINEX spec how to do.

Good luck,

Sam

oppler[s]);
y-doppler[s]) *
(from
range + clock
clock correction *
her

Dear Sam,

i looked at the RINEX spec, but and tried it, but only when i use
phase[s] +=3D Adjust * (L1Frequency-doppler[s]);
pseudorange[s] +=3D Adjust * (L1Frequency-doppler[s]) * L1WaveLength;

i get resnable solution

i understand L1Frequency-doppler[s] is the change in doppler, but at
RINEX specs. they ignor "-doppler[s]".
Is it neglatable? from my tests, no.

Then, am i doing something wrong?

Regards

wrote:
r
-doppler[s]);
ncy-doppler[s]) *
n (from
dorange + clock
+ clock correction *
other

Hi Hanan,

According RINEX a decreasing range between staellite and receiver is
negative
in delta pseudorange [m/s] and
positive in delta carrier [cy/s] and Doppler [cy/s]. Not all receivers
stick to this
sign definition, therefore you always have to check how the change in
range
has been output by th manufacturer. As far as I can remember u-Blox
sticks
to the RINEX spec.

Hope this helps,

Sam