Specifications

VP ONCORE COMMAND REFERENCE
6 CHANNEL SATELLITE RANGE DATA OUTPUT
MESSAGE (@@Bg)
continued
In the discussions that follow, the subscript (
k
) refers to the current
measurement data, and the subscript (
k-1
) refers to the previous (1
second old) data. The user can convert the above message into
pseudorange and pseudorange rate for each satellite by using the
following formulas:
Conversion Pseudorange (in meters) = (GPS local time - GPS satellite time) * SOL
Formulas Note: Not corrected for possible End-Of-Week Rollovers.
Pseudorange Rate (in meters per second) = K2 * (ICP
k
– ICP
k-1
)
ICP is the integer and fractional part of ICP treated as a 32 bit unsigned
quantity Use 32 bit unsigned integer subtraction to avoid rollovers.
Absolute Carrier Phase at measurement epoch in degrees = K4 * ICP
f
The GPS satellite time used in the first equations for the computation of
pseudorange is the same value that the Oncore uses internally. This
satellite time value combines code and carrier information and has been
pre-smoothed using carrier aided filtering with a very narrow-band (0.005
Hz) low-pass filter algorithm. The user has access to the unfiltered raw
code phase via the following:
Raw Code Phase (in meters) = K1 * RCP - K2 * ICP
f
+ K3 * K5 * CD
where:
RCP is the raw code phase from the message
ICP
f
is the fractional part of the integrated carrier phase
CD is the code discriminator output from the message
K5 is a variable code discriminator calibration constant
Code discriminator calibration constant: When tracking satellites, the
receiver causes the raw code phase to move back and forth once per
second in discrete steps of 1 code phase quantum. One code phase
quantum is equal to 55 carrier cycles, or about 10.4662 meters. This
intentional dither allows the receiver to calibrate the output of the code
discriminator.
87 Synergy Systems, LLC 05OCT01