Global Positioning System Reference
In-Depth Information
postnavigation.m
calculate
pseudoranges
find satellite
positions and
clock offsets
least squares
filter (az, ele,
DOP,
X
,
Y
,
Z
)
store
results
return
FIGURE A.4. Flow diagram for the position computation.
elevationMask
Satellite elevation mask. Sets the minimum elevation angle for
a satellite to be included in the computation of the position solution. Sig-
nals from satellites at low elevation angles are contaminated by large atmo-
spheric errors.
UTMzone
UTM Zone to be used for the coordinate transformation (ECEF to
UTM). This is an integer that depends on the location of the receiver.
truePosition
If an accurate position of the receiver antenna is known, then the
E
asting,
N
orthing, and
U
pping coordinates of the antenna can be specified.
These coordinates will be subtracted from the ones computed by the soft-
ware receiver, and the result will be plotted.
You may enter
(
E
,
N
,
U
)
either as approximate coordinates or as zeros.
A.5.1 Pseudorange Computation
This function computes pseudoranges for all tracked satellites. Pseudoranges are
not computed for nontracking channels, for channels that have undetected pream-
ble, or for channels that have detected a parity error in the navigation data; see
Figure A.5.
The input for the function is the output of the in-phase prompt correlator. The
function also needs precise code-phase information. Typically, both inputs are
read from the structure
trackResults
.
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