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Document Title: 34
User’s Manual for the GPS Orion-S/-HD Receiver
Document No. Issue 1.0
GTN-MAN-0110 June 22, 2003
DLR/GSOCNo part of this document shall be reproduced in any form or disclosed to third parties without prior authorization.
4.4.1.7 F41 – Pseudorange and Range Rate (Smoothed)
Carrier phase smoothed pseudoranges and carrier phase based range rate measurements
for each of the twelve channels are provided in the F41 message. The data are identical to
those employed by the receiver in the computation of the navigation solution for the same
epoch.
MsgID Chars. Format Description
F41 337
Pseudorange and range rate (smoothed)
1
x <STX>
3
xxx Message Id (=F41)
4
xxxx GPS week
12
xxxxxx.xxxxx GPS seconds of week [s] (GPS time of observ. using current clock model)
2
xx GPS-UTC [s]
12
xxxxxx.xxxxx TIC time [s]
Repeated for each of 12 channels
2
xx PRN
13
xxxxxxxxxx.xx Pseudorange [m] (smoothed)
9
sxxxxx.xx Range rate [m/s] (from carrier phase)
1
x Validity flag
2
xx Checksum
1
x <ETX>
Notes:
• Due to carrier phase smoothing, the pseudoranges provided in the F41 message ex-
hibit a smaller short term noise (ca. 0.1 m) than the raw pseudorange measurements
(ca. 1 m; provided in F42). Absolute errors are of similar size, however, due the code-
carrier divergence in dispersive media (ionosphere) that necessitates regular resets
of the filter/smoother.
• The range rate measurements are obtained by fitting a quadratic polynomial to three
adjacent carrier phase measurements over an interval of 2 x 0.1 s and evaluating its
derivative at the latest instant. This procedure is rigorously correct up to constant line-
of-sight accelerations and is also well applicable for low-Earth orbiting satellites.
Some errors may, however, arise in phases of extreme jerk that are e.g. encountered
during sounding rocket missions.
• Measurements are nominally collected once full frame lock has been achieved on the
tracking channel. In addition, measurements can already be provided in carrier lock if
a valid navigation solution is available to perform the required synchronization of raw
correlator readings. To prevent bad measurements from entering the navigation solu-
tion, measurements are only tagged valid from 10 s after frame lock onwards in the
Orion-S receiver.
Example:
<STX>F411079482689.0000013 6684.19332 3 20046984.19 -2011.46110 23977589.65 +
6925.48117 21815655.29 +5625.87126 24265035.99 +7015.39122 0.00 +0.
001 2 27964124.58 -140.94113 0.00 +0.00118 25350034.35 –4207.27119
0.00 +0.001 1 23326544.73 -703.39121 26574208.50 -758.06115
0.00 +0.00147<ETX>