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RoyalTek REB-3000 User Manual

Page 42

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RoyalTek RGM-3000/REB-3000
GPS Module Operational Manual)

37

Phase Loss
Count:

The number of time the phase lock fell below the threshold between the
present code phase sample and the previous code phase sample. This task is
performed every 20 ms (max count is 50).

Integration
Interval:

The time in ms for carrier phase accumulation . This is the time difference (as
calculated by the user clock) between the Carrier Phase(current) and the
Carrier Phase(previous).

Track Loop
Iteration:

The tracking Loops are run at 2 ms and 10 ms intervals. Extrapolation values
for each interval is 1 ms and 5 ms for range computations.

Calculation of Pseudo-Range

Measurements

The pseudo-range measurement in meters

can be determined from the raw track data

by solving the following equation:

Pseudo-range (PR) = {Received Tine

(RT) – Transmit Time (TT)} * C

where C = speed of light

The following variables from the raw track

data are required for each satellite:

Bit Number (BN) – 50 bits per second

Millisecond Number (MSN)

Chip Number (CN)

Code Phase (CP)

Receiver Time Tag (RTTag)

Delta Carrier Phase (DCP)

The following steps are taken to get the psr

data and carrier data for each measurement

epoch.

1. Computation of initial Receiver

Time(RT) in seconds. Note-Where the

initial arbitrary value chosen at start

up to make the PR reasonable

(i.e.,set equal to TT+70ms) and then

incriminated by one second for each

measurement epoch.

2. Computation of Transmit Time (TT) in

seconds.

3. Calculate Pseudo-range at a common

receiver time of the first channel of

the measurement data set. Note-All

channel measurements are NOT

taken at the same time. Therefore, all

ranges must be extrapolated to a

common measurement epoch. For

simplicity, the first channel of each

measurement set is used as the

reference to which all other

measurements are extrapolated.

4. Extrapolate the pseudo-range based

on the correlation interval to improve

precision.

5. Compute the delta range.

If the accumulation time of the Dalta Carrier

Phase is 1000 ms then the measurement is

valid and can be added to the previous Delta

Carrier Phase to get Accumulated Carrier

Phase data. If the accumulation time of the

Delta Carrier Phase is not equal to 1000 ms

then the measurement is not valid and the

accumulation time must be restarted to get

Accumulated Carrier Phase data.

Response :Software Version

String – Message I.D.6

Output Rate:Response to polling message

Example:

A0A20015 – Start Sequence and Payload

Length

0606312E322E30444B495431313920534

D0000000000-Payload

0382B0B3 – Message Checksum and End

Sequence

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