Capturing raw Observation (RXM-RAWX) & Navigation (RXM-SFRBX) data from u-blox receivers using gnssstreamer

[semuadmin]

A common use case for these GNSS utilities is to capture an extended series of raw Observation (UBX RXM-RAWX) and Navigation (UBX RXM-SFRBX) messages from a u-blox receiver (e.g. ZED-F9P or ZED-X20P), typically as a precursor to RINEX conversion and PPK processing.

Here, for example, is a gnssstreamer CLI command* which can be used to a) configure an F9P or X20P to output the requisite UBX message cohort, and b) record the binary data output to a file (in this example, /dev/ttyACM0 represents the device's USB port):

gnssstreamer -C gnssstreamer_zedf9p_raw.conf

The gnssstreamer_zedf9p_raw.conf text file contains a series of command line arguments (amend as required, but ensure format=2):

port=/dev/ttyACM0
baudrate=460800
timeout=3
verbosity=2
format=2
cliinput=5
input=/home/semuadmin/Downloads/pygpsconfig_zedf9p_raw.bin
clioutput=1
output=/home/semuadmin/Downloads/pygpsdata_zedf9p_rawlog.ubx

(for further command line options, type gnssstreamer -h or refer to the examples in the README)

The pygpsconfig_zedf9p_raw.bin binary file contains a series of UBX CFG-VALSET configuration commands previously recorded using PyGPSClient's 'Configuration Command Recorder' facility:

The CFG-VALSET configuration commands would typically include:

1. set measurement interval to 1000ms (1 Hz) - CFG_RATE_MEAS = 1000
2. set UART1 and UART2 baud rates to 460800 - CFG_UART1_BAUDRATE = 460800, etc. (NB: do this even if you're using the USB port)
3. disable all NMEA messages on USB - CFG_USBOUTPROT_NMEA = 0
4. enable UBX NAV-POS, NAV-SAT, NAV-DOP, NAV-HPPOSLLH, RXM-RAWX and RXM-SFRBX messages on USB - CFG_MSGOUT_UBX_RXM_RAWX_USB = 1, etc.

The output will be captured in the pygpsdata_zedf9p_rawlog.ubx file.

* If you wanted to start the above CLI command under Linux as a unattended 'daemon' and just leave it running in the background, you could use something like this (to terminate, use the Linux kill or pkill command):

setsid gnssstreamer -C gnssstreamer_zedf9p_raw.conf >gnssstreamer.log 2>&1 < /dev/null &

(I have this set up as an alias in my .zshrc profile)

Alternatively, you could set it up to run as a systemd service.