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iSXblue/SXBlue II GNSS Series Technical Reference Manual
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Table 5-22 GRS Data Message Defined
Field
Description
Hhmmss.ss
UTC time of the GGA or GNS fix associated with this sentence
Y
Mode 0: residuals were used to calculate the position given in the matching GGA or GNS
sentence
Mode 1: residuals were recomputed after the GGA or GNS position was computed
x.x
Range residuals, in meters, for satellites used in the navigation solution. Order matches
order of satellite ID numbers in GSA sentence. When GRS is used, GSA and GSV are
generally required
5.9.12
RD1 Data Message
The RD1 message contains diagnostic information for SBAS operation. The table below breaks down the
RD1 data message into its components. This message has the following format:
$RD1,SecOfWeek,WeekNum,FreqMHz,DSPLocked,BER-BER2,AGC,DDS,Doppler,DSPStat,
ARMStat,DiffStatus,NavCondition *cc<CR><LF>
Table 5-23 RD1 Data Message Defined
Field
Description
SecOfWeek
The second of GPS week (may be a couple of seconds old)
WeekNum
The GPS week number
FreqMHz
The L-band frequency in MHz (1475.4200 is used for SBAS)
DSPLocked
1 if DSPStat = 1B or 1F
BER-BER2
Bit error rate – bit error rates are given for both SBAS satellites being tracked
AGC
L-band Signal strength
DDS
0.0 for SBAS
Doppler
0 for SBAS
DSPStat
A status bit mask for the DSP tracking of SBAS
ARMStat
A status bit mask for the ARM GPS solution
DiffStatus
The SBAS PRN of the satellite in use
NavCondition
A series of hex character fields, which is read from right to left, with each field
representing the number of GPS satellites satisfying a certain condition, all of which
conditions are required if the satellite is to be used in the solution
*cc
Checksum
<CR><LF>
Carriage return and line feed
The following table describes the DSP status. The DSP status should be 17, 1B, or 1F when SBAS
tracking has been achieved.
DSP Status
Field
Description
01
Carrier lock
02
BER is ok on at least one SBAS satellite
04
Frame synchronization has been achieved on the second satellite
08
Frame synchronization has been achieved on the first satellite
10
Carrier lock
The following table describes the ARM status.