GSV GPS-702 User manual

GSVGPS Silicon Valley
1131 Seena Avenue, Los Altos, CA 94024, USA 1-650-961-8250
1-650-961-7461 (FAX)
GSV4004B
GPS IONOSPHERIC SCINTILLATION & TEC MONITOR
(GISTM)
USER'S MANUAL
(1 August 2007)

TABLE OF CONTENTS
Getting Started .................................... 1
Installation .................................... 2
Running GSV4004B .................................... 3
GSV4004B Scintillation/TEC Logs .................................... 3
GSV4004B Specific Commands .................................... 8
Tracking SBAS (WAAS, EGNOS, MSAS) SVs ………………………… 9
C/A-To-P Biases ………………………… 10
SLOG Details .................................... 11
Off-Line Utility Programs .................................... 14
Suggested Scintillation Analysis Procedures ………………………… 17
Directions For Loading New Firmware 23
Appendix A – EuroPak-3M and L1/L2 Antenna
Data Sheets A-1
Appendix B – Example SLOG Script for
Periodic Files for 60-Second Logs ………………………… B-1
Appendix C – Example SLOG Script for
Recording High-Rate (50-Hz) Logs ………………………… C-1
Appendix D – ISMVIEW4 Off-Line Utility
Program ................................... D-1
Appendix E – SBAS PRN Assignments ………………………… E-1
LIST OF TABLES
I. Specific GSV4004B Data Logs .................................... 3
II. RAWSINB Data Log - Message ID = 327 .................................... 5
III. ISMRB Data Log - Message ID = 274 .................................... 6
IV. C/A-to-P SV Biases (May 2003) ………………………… 11
V. Threshold Parameters Specified in
ScintRaw Script .................................... 12
VI. PARSEISMR Extracted Data Fields ………………………… 14
VII. PARSESIN Extracted Data Fields ………………………… 15
D.1. Key-Stroke Commands .................................... D-3
D.2. Extracted Data Fields .................................... D-4
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LIST OF FIGURES
1. GSV4004B GPS Ionospheric Scintillation and TEC Monitor ......... 2
2. Example Phase Sigma Plots in a Non-Scintillation
Environment for GPS PRNs ......... 18
3. Example Phase Sigma Plots in a Non-Scintillation
Environment for an SBAS GEO ......... 19
4. Example Corrected S4 Plots in a Non-Scintillation
Environment for GPS PRNs ......... 19
5. Example Corrected S4 Plots in a Non-Scintillation
Environment for an SBAS GEO ......... 20
6. Example Estimated Multipath Error Plotted Against Corrected
S4 in a Non-Scintillation Environment for GPS PRNs ......... 20
7. Example Estimated Multipath Error Plotted Against Corrected
S4 in a Non-Scintillation Environment for an SBAS GEO ......... 21
8. Example Detrended Raw Amplitude and Phase Data in a
Non-Scintillation Environment for GPS PRN 2 Where S4
Exceeded 0.3
......... 22
D.1. ISMVIEW4 Main Menu ......... D-1
D.2. ISMVIEW4 Display ......... D-2
D.3. ISMVIEW SV ISMR Data Extraction ......... D-3

GSVGPS Silicon Valley
GETTING STARTED
INTRODUCTION
This manual covers the operation of GPS Silicon Valley’s GPS Ionospheric Scintillation and TEC Monitor
(GISTM) system Model GSV4004B. The GSV4004B, with its optional antenna, consists of three major
components: an L1/L2 GPS Antenna (NovAtel’s Model 532, 533 or GPS702), a GPS receiver (NovAtel’s
EuroPak-3M) and a power supply with various interconnecting cables. The EuroPak-3M enclosure houses the
GPS receiver and a low phase noise oven-controlled crystal oscillator (OCXO) that is required for monitoring
phase scintillation. The GPS receiver, the Euro-3M, with modified software (firmware), can track up to 11 GPS
signals signal at the L1 frequency (1575.42 MHz) and the L2 frequency (1227.6 MHz). It measures phase and
amplitude (at 50-Hz rate) and code/carrier divergence (at 1-Hz rate) for each satellite being tracked on L1, and
computes TEC from combined L1 and L2 pseudorange and carrier phase measurements. The 11th and 12th
dual channels are configured as SBAS satellite tracking channels, and to measure a noise floor for C/N0and S4
correction computations. The 11th dual channel is designated as Channels 10 and 11. The 12th dual channel is
designated as Channel 12. The last half of the 12th dual channel is the noise floor channel. Thus, there are 10
GPS channels (Channel 0 through Channel 9) and 3 SBAS-GEO channels (Channels 10, 11 and 12).
Scintillation measurements are also available on all 3 SBAS-GEO channels. However, the phase scintillation
parameters are somewhat degraded because the SBAS networks are steering the phase of the signal.
Older optional firmware loads assigned only one SBAS-GEO channel with 11 GPS channels. That option is no
longer available.
See Appendix A for specifications for the EuroPak-3M receiver and the L1/L2 antennas. Two CDROMs are
distributed with the GSV4004B – a NovAtel CDROM and a GSV Utilities CDROM. A preliminary manual for the
EuroPak-3M is included on the GSV Utilities CDROM. However, this EuroPak-3M manual should only be used
for the hardware and installation descriptions. The NovAtel data logs from the GSV4004B are based upon
NovAtel’s OEM4 receiver, as the GSV4004B firmware is based upon OEM4 firmware. The OEM4 manuals are
also included on the GSV Utilities CDROM. This GSV4004B manual only augments the NovAtel manuals.
The primary purpose of the GSV4004B GISTM is to collect ionospheric scintillation and TEC data for all visible
GPS satellites (up to 10), and up to 3 SBAS-GEO satellites, and output data logs, called ISMRB or ISMRA, to a
serial port in either binary or ASCII format. Either of two (NovAtel GPSolution4 or SLOG) programs can be used
to control the GSV4004B operations, but SLOG is recommended for collecting scintillation logs. The
GSV4004B’s Data Logging operation can be controlled to collect the ISMR data logs that are generated every
minute. Details of the ISMR data are presented in the GSV4004B Scintillation/TEC Log section. Another off-
line PC-based program, ISMVIEW4.EXE, may be used to review the ISMR data. Raw 50-Hz phase and
amplitude data logs are also available.
In addition, data extraction programs are supplied for extracting records from the binary files. They are
described within. Example source C++ code is also supplied so the users can write their own extraction
programs.
This manual augments the NovAtel manuals provided with the GSV4004B. Minimum PC requirements are
specified in those manuals. If the high-speed phase and amplitude data logs are to be collected, GSV
recommends using an external high-speed serial port device as a buffer between the GSV4004B and the PC.
The GSV4004B can have serial port output rates as high as 230 kBaud. An example of such a high-speed
serial device is the Inside Out Networks Edgeport USB Expansion Module (www.ionetworks.com). Test results
have indicated that certain PC serial ports cannot cope with the high-speed logs.
From time-to-time, there may be GSV4004B firmware upgrades. If there is an upgrade, it will be distributed free
of charge, most likely via email. A section in the manual is devoted to instructions for loading the upgraded
firmware.
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GSVGPS Silicon Valley
INSTALLATION
INSTALLING HARDWARE
Figure 1 presents the GSV4004B and an optional antenna (GPS-702 or GPS-702GG)1. The GSV4004B Rear
Panel is described in the NovAtel manual for the EuroPak-3M enclosure. See the applicable NovAtel manuals
for hardware installation instructions.
GSV4004B GPS-702 or GPS-702GG L1/L2 Antenna
Figure 1. GSV4004B GPS Ionospheric Scintillation and TEC Monitor and Optional Antenna
INSTALLING SOFTWARE
The NovAtel GPSolution4 software program is distributed on the NovAtel CDROM provided with the
GSV4004B. It can be installed using the “autorun” feature on the CDROM. Then, simply execute the program
from Windows and follow instructions. Consult the NovAtel manuals for operating instructions.
After installation, set up GPSolution4 to recognize the special GISTM logs as follows:
1. Open GPSolution4, and open the appropriate GSV4004B serial port (computer port, not the receiver
port).
2. Select "Update All Convert4 Log Definitions" from the main menu.
3. “Updating Convert4 Conversion Definitions” will appear in the status bar. Once updated, GPSolution4
and Convert4 will be aware of the ISM logs.
4. These procedures are not necessary for subsequent execution of GPSolution4 and Convert4.
GPSolution4 is no longer supported by NovAtel, so it is recommended that SLOG and the parsing utilities
defined herein be used (or other programs developed by the user). The SLOG and other utility programs are
distributed on the second utilities CDROM provided with the GSV4004B. For SLOG and the utility programs,
simply copy all files from the CDROM to a sub-directory you have selected on your hard disk. The SLOG
program manual and example script files used by SLOG are provided on the CDROM, as is this manual.
1The GSV-702 antenna has been discontinued by NovAtel. The GSV-702GG replaces it and covers the GLONASS band.
However, GLONASS satellites are not tracked by the GSV4004B.
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GSVGPS Silicon Valley
RUNNING THE GSV4004B
INITIALIZING THE GSV4004B
The GSV4004B initializes itself upon power-up and begins to acquire satellites using default information. It
automatically locks to the 10 MHz OCXO internal to the enclosure. However, the following non-factory
configuration command should be sent to the receiver to ensure that the GSV4004B provides valid low-phase
noise scintillation parameters:
CLOCKADJUST DISABLE
to disable receiver hardware clock adjustments (to GPS time). These clock adjustments could cause jumps in
the phase data. The downside to this is that clock drift over a very long period of time could cause the
receiver’s time offset from GPS to exceed its limits, but unlikely. Since the clock adjustments should be very
small, the user may chose to not use this command.
Other specific GSV4004B commands controlling filter bandwidths are described later. Default values are set in
the GSV4004B.
RECORDING DATA ON HARD DISK
Either NovAtel’s GPSolution4 or SLOG programs can be used to select data logs from the GSV4004B. These
logs will be continuously recorded to a specified disk file. (It is recommended that SLOG be used to avoid
possible Windows crashes. However, GPSolution4 is excellent for monitoring general receiver performance in
a Windows GUI environment, especially during installation. SLOG is a Windows based program as well that is
executed using the Command Prompt; it does not have a Windows GUI.) The use of SLOG is described in the
SLOG Details Section.
GSV4004B SCINTILATION/TEC LOGS
In addition to the data logs described in the NovAtel manuals, the GSV4004B supports the scintillation/TEC data
logs listed in Table I. For each selected data log, you may also select one the following trigger methods:
Table I. Specific GSV4004B Data Logs
LOG ID BYTE COUNT DESCRIPTION
RAWSINB 327 H + 4 + (n * 420) GISTM 50-Hz phase and amplitude data, and 1-Hz TEC data
(rate = 1 per sec)
DETRSINB 326 H + 4 + (n * 420) GISTM detrended RAWSINB data (rate = 1 per sec)
ISMRB 274 H + 4 + (n*152) GISTM main data record (rate = 1 per 60 sec)
Note: n is the number of SVs being tracked.
RANGEB and RANGEA Data Logs. These NovAtel logs will be slightly different that specified in the
OEM4 manual in that there will be an odd number of observations when a GEO is tracked in the 12th channel
(Channel 11a). Nothing is reported for the noise-floor half of the 12th channel (Channel 11b).
DATA LOG FORMATS
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These three data logs, ISMRB, RAWSINB and DETRSINB, are peculiar to the GSV4004B. Please refer to
NovAtel's GPS OEM4 Receiver User Manuals for detailed descriptions of other data logs.
BINARY LOG STRUCTURE
The structure of the binary messages is given in the NovAtel manuals.
RAWSINB Data Log. The receiver collects raw phase measurements and raw amplitude measurements at
50 Hz rate (i.e. 50 sets of measurements a second) and stores them in the binary RAWSINB data log every
second on the second. Continuous data will be recorded when the ONTIME trigger is specified with 1.0 second
period. Each log contains data blocks for all the satellites being tracked. Each data block contains 50 sets of
data; the first set is at time specified in Time of Week (TOW), the second set at TOW+0.02 seconds, and so on.
The ADR (phase) in this log is that of the tracking model. It contains frequencies up to the tracking loop
bandwidth (default at 10 Hz). This log also includes raw 1-second TEC and ΔTEC data. The format of the
RAWSINB data logs is given in Table II.
The scale factor of the raw power measurements is meaningless. This is because the actual receiver and
antenna gains are unknown. In the end, this does not matter because subsequent detrending and forming of
S4 will normalize the measurements.
The raw phase measurements include satellite motion, the rate of change of the ionosphere and satellite and
receiver oscillator drift. Thus, observation scintillation in the measurements without detrending is not possible,
although the use of FFT programs with windowing may be used without detrending.
DETRSINB Data Log. The DETRSINB data log has the Message ID of 326. The data log is the same
format as the RAWSINB log, with the exception that the data it contains is the receiver-detrended scintillation
data, and the scale of the power measurements is Ratio * 1048576 (ratio of raw to low-pass filtered). The
DETRSINB data logs should not be requested at the same time the RAWSINB data logs are requested to
prevent port overload. The GSV4004B will ignore the second request unless the original request is canceled
(un-logged).
DETRSINB data logs are different if the “60-second averaging” amplitude detrending is selected. If this 60-
second averaging is selected, the detrended data is simply the raw data divided by the previous 1-minute raw
data average. See more detail on this below under the discussions of the Filter Bandwidth command. Further
detrending (by averaging) is recommended to remove the ambiguity between 60-second intervals.
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Table II. RAWSINB Data Log - Message ID = 327
Message byte count = H + 4 + (n * 420) (n = the number of SVs being tracked)
Field # Data Bytes Format Units Offset
1 header H 0
2 Number of SV observations 4 integer H
For First SV observation
3 PRN 2 integer H+4
4 reserved 2 H+6
5 L1 TEC at TOW 4 float TECU H+8
6 L1 ΔTEC (1-sec) at TOW 4 float TECU H+12
7 First L1 ADR 8 double cycles H+16
8 L1 ΔADR for TOW + 0.00 4 signed integer millicycles H+24
9 L1 Power for TOW + 0.00 4 unsigned integer (nbp-wbp)*
/10000 H+28
10 L1 ΔADR for TOW + 0.02 4 signed integer millicycles H+32
11 L1 Power for TOW + 0.02 4 unsigned integer (nbp-wbp)*
/10000 H+36
...
107 L1 ΔADR for TOW + 0.98 4 signed integer millicycles H+41
8
108 L1 Power for TOW+ 0.98 4 unsigned integer (nbp-wbp)*
/10000 H+42 0
109... For Next SV Observation
* See text regarding scale factor (units) for detrended power.
ISMRB Data Log. Both the RAWSINB and the DETRSINB data logs described above contain only raw or
detrended-raw measurements (TEC, TEC-phase, phase and amplitude). They are available for diagnostic or
analytical purposes. The user must supply data analysis programs to process this raw data. A data reduction
program is supplied with the GSV4004B ISM to convert the data to a convenient ASCII format. However, the
receiver automatically reduces these raw measurements every minute on the minute and stores the results in
the ISMRB data log. The GSV4004B provides continuous data at the specified ONTIME (or ONNEW) trigger
with a 60 second period. Each log contains data blocks for the all satellites being tracked, including an SBAS
GEO, if one has been assigned and is visible. The format of the ISMRB data log is given in Table III.
TEC Calculations TEC (Total Electron Content) is a measure of the number of electrons along the path from
the satellite and is reported in TEC Units (TECU = Electrons *10-16). The number is proportional to the
ionospheric delay between L1 and L2 signals.
TEC = [9.483 * (PRL2 – PRL1 - ΔC/A-P,PRN) + TECRX + TECCAL ] TECU
where:
PRL2 is the L2 pseudo-range in meters
PRL1 is the L1 pseudo-range in meters
ΔC/A-P,PRN is the input bias between SV C/A- and P-code code chip transitions in meters (see below)
TECRX is the TEC result due to internal receiver L1/L2 delay
TECCAL is the user defined TEC offset
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GSVGPS Silicon Valley
Table III. ISMRB Data Log - Message ID = 274
Message byte count = H + 4 + (n * 152) (n = number of SVs being tracked)
Field # Data Bytes Format Units Offset
1 Header H 0
2 Number of SV observations 4 integer N/A H
For First SV observation
3 PRN 2 integer N/A H+4
4 SV Azimuth angle1 4 float degrees H+8
5 SV Elevation angle1 4 float degrees H+12
6 C/N08 double dB-Hz H+16
7 Total S4 8 double dimensionless H+24
8 Correction to total S4 8 double dimensionless H+32
9 1-second phase sigma 8 double radians H+40
10 3-second phase sigma 8 double radians H+48
11 10-second phase sigma 8 double radians H+56
12 30-second phase sigma 8 double radians H+64
13 60-second phase sigma 8 double radians H+72
14 Average of Code/Carrier
divergence 8 double meters H+80
15 Sigma of Code/Carrier Divergence 8 double meters H+88
16 TEC at TOW - 45 4 float TECU H+96
17 ΔTEC from TOW - 60 to TOW - 45 4 float TECU H+100
18 TEC at TOW - 30 4 float TECU H+104
19 ΔTEC from TOW - 45 to TOW - 30 4 float TECU H+108
20 TEC at TOW - 15 4 float TECU H+112
21 ΔTEC from TOW - 30 to TOW - 15 4 float TECU H+116
22 TEC at TOW 4 float TECU H+120
23 ΔTEC from TOW - 15 to TOW 4 float TECU H+124
24 L1 Lock time 8 double seconds H+128
25 Channel status 4 integer H+136
26 L2 Lock Time 8 double seconds H+140
27 L2 C/N08 double dB-Hz H+148
28... For Next SV Observation
Note 1: Data may also be included for SVs that are unhealthy. However, the Azimuth and Elevation may be set
to 0. All scintillation data will still be valid. The TEC values may be set to 0 because of the
unavailability of the Tau_GD value.
TECRX is the nominal L1/L2 receiver delay (converted to TECU) hard-coded as a data base parameter, and
TECCAL is an input parameter supplied by the user, since the receiver differential delay may change slightly with
time, and will be different from unit-to-unit. The units are calibrated against WAAS prior to shipment and the
TECCAL value is indicated on the bottom of the unit and on its shipping carton (for shipments after 1 July 2002).
The TEC is also corrected for satellite inter-frequency biases (Tau_GD – see ICD-GPS-200D), but not for the
SV C/A-to-P biases. These biases are available on a JPL website (see a later section in this document) and
can be input to the GSV4004B during initialization (see below). As an alternative, the values of these biases
can be converted to TECU and added to the logged TEC values.
ΔTEC is based upon carrier phase measurements at L1 and L2. For an ionospheric delay measured in L1
carrier cycles, the total electron content becomes
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GSVGPS Silicon Valley
ΔTEC = (1.1723 ΔPRL1,carrier) TECU
over the 1-second interval, where
ΔPRL1,carrier = 1.54573 (ΔADRL1 – ΔADRL2) cycles
measured over the 1-second interval (RAWSINB and DETRSINB) or over a 15-second interval (ISMRB).
Phase. As mentioned above for the RAWSINB data log, the receiver collects 50 raw phase measurements a
second. The raw phase measurements are first detrended with a 6th-order Butterworth high-pass filter (with a
user-specified cutoff frequency). Then, for every minute on the minute, the statistics of the residuals (of the
previous 3,000 detrended phase measurements) are computed over periods of 1 second, 3 seconds, 10
seconds, 30 seconds and 60 seconds. Thus, for every 60 seconds, 5 values (1-sec, 3-sec, 10-sec, 30-sec
and 60-sec phase sigma’s) are stored in ISMRB data log along with the time tag (in week number and time
of week).
Amplitude. The raw amplitude measurements are detrended (by normalization), either with a 6th-order
Butterworth low-pass filter output (with a user-specified cutoff frequency), or with the measurement average
over the 60-second interval (if the user-specified cutoff frequency is 0). The latter method is the default method
if no cutoff frequency is specified. Then, the total S4, which includes S4 due to the effects of ambient noise
(and multipath), is computed over the same 60-second interval as the phase parameters. The receiver also
computes the correction to the total S4, which is the effect of ambient noise, based upon the average of the
raw 1-Hz C/N0values over the same 60-second intervals.
Code/Carrier Divergence. The receiver also collects raw code/carrier divergence (difference between
code and carrier pseudorange) every second. The average and standard deviation of the code/carrier
divergence are then computed every minute on the minute. These values are indicative of multipath (and noise)
activity and can be used to distinguish between S4 due to multipath (and noise) and S4 due to scintillation,
since there is no code/carrier divergence due to scintillation. A method for using the code/carrier divergence
standard deviation is provided below.
L1 Lock Time. The L1 Lock Time indicates how long the receiver has been locked to the carrier phase on
the L1 signal. Since the phase-detrending high-pass filter has to be reinitialized whenever lock is lost, all phase
parameters (sigmas) should be discarded for any Lock Time less than 180-240 seconds (for a 0.1 Hz
bandwidth) to allow the detrending filter to re-settle. For other bandwidths, this time may vary inverse-
proportionally to the bandwidth. For the S4 parameters, it suffices to only discard data for any Lock Time less
than 60 seconds. S4 may also be valid for Lock Time less than 60 seconds since the power measurements are
non-coherent measurements that do not require phase lock. However, on rare occasions, total signal lock could
have been lost, so the use of S4 for Lock Time less than 60 seconds should be used with caution. However, in
those cases, the code/carrier divergence measurements could be used to discard the data.
L2 Lock Time. The Lock Time indicates how long the receiver has been locked to the carrier phase on the
L2 signal. It is an indicator of the validity of the TEC measurements. As with the L1 phase data, short Lock
Time data should be discarded.
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