GPSRINEX(1)

NAME
gpsrinex - Read data from gpsd, convert to RINEX, and save to a file.

SYNOPSIS

gpsrinex [OPTIONS] [server[:port[:device]]]

gpsrinex -h

gpsrinex -V

DESCRIPTION

gpsrinex is a tool to connect to gpsd and output the received raw measurements as a RINEX observation file. This is useful for sending raw measurements (pseudorange and carrierphase) from gpsd to a Precise Point Positioning (PPP) program or service.

gpsrinex does not require root privileges, but may be run as root. Some of the examples in this file may not work when run under sudo. It can be run concurrently with other tools connecting to a local or remote gpsd without causing problems.

gpsrinex needs the GNSS receiver to be sending raw measurements to gpsd. Only a few GNSS have this capability. In addition, the gpsd driver for that GNSS must support raw mode. Currently only the u-blox driver has this support. Only a few u-blox 8, 9, and 10, receivers implement the required UBX-RXM-RAWX message. The NEO-M8T is known to work, but requires configuration with ubxtool.

Before using ubxtool be sure to set the UBXOPTS environment variable with the correct protocol version for your u-blox receiver. If your protocol version is 32.00, you would do this:

    export UBXOPTS="-P 32.00"

RINEX has its own definitions and abbreviations. Be sure to consult their documentation. An observation file (.obs) contains data sets, called epochs, that contain the pseudorange and carrierphase for each satellite seen.

gpsrinex by default will acquire 20 epochs spaced apart by 30 seconds. That will take 10 minutes to complete. Most users consider the 30 second interval to be optimal. Many PPP programs require at least 1 or 2 hours data, but no more than 24 or 48 hours of data. Most users consider 4 to 6 hours of data as a minimum for good accuracy. Additional hours will not yield much improvement.

The output will consist of one RINEX observation file that is ready to be read by your PPP program. The default filename will be in the form: gpsrinexYYYYjjjDHHMM.obs. You can override this filename with the -f option.

Optionally a server, TCP/IP port number and remote device can be given. If omitted, gpsrinex connects to localhost on the default port (2947) and watches all devices opened by gpsd.

OPTIONS

-?, -h, --help
    Print a usage message and exit.

-D LVL, -debug LVL
    Set debug level to LVL.

-f OUTFILE, --fileout OUTFILE
    save RINEX into FILE.

-F INFILE, --filein INFILE
    Read GPS JSON from file, not from a live gpsd.

-g CODES, --gnss CODES
    Only output a GNSS system if the RINEX code is in CODES. C = BeiDou, E = Galileo G = GPS, I = IRNSS, J = QZSS, R = GLONASS, S = SBAS.

-i SECS, --interval SECS
    wait [interval] seconds between epochs. The interval can be specified to the millisecond. OPUS accepts intervals of 1, 2, 3, 5, 10, 15 or,30 seconds. OPUS then reduces the data to 30 second intervals. Default is 30.000.

-n COUNT, --count COUNT
    Causes COUNT epochs to be output. OPUS requires a minimum af 15 minutes, and a maximum of 48 hours, of data.

-V, --version
    makes gpsrinex print its version and exit.

The following options set strings that are placed in the generated RINEX 3 obs file. They do not change how gpsrinex computes anything.

--agency AGENCY
    The name of the agency creating the current file.

--ant_num NUMBER
    The antenna serial number.

--ant_type TYPE
    The antenna type.

--comment CMT
    Free form comment.

--marker_name NAME
    The marker name.

--marker_type TYPE
    The marker type

--observer OBSERVER
    The name of the observer (you).

--rec_num NUM
    The receiver serial number.

--rec_type TYPE
    The receiver type.

--rec_vers VERS
    The receiver version.

The following options set floating point numbers that are placed in the generated RINEX obs file. They do not change how gpsrinex computes anything.

--ant_e EASTING
    The antenna easting from marker in meters.

--ant_h HEIGHT
    The antenna height from marker in meters.

--ant_n NORTHING
    The antenna northing from marker in meters.

ARGUMENTS

By default, clients collect data from the local gpsd daemon running on localhost, using the default GPSD port 2947. The optional argument to any client may override this behavior: [server[:port[:device]]]

For further explanation, and examples, see the ARGUMENTS section in the gps(1) man page

EXAMPLES

Example 1:

Create a 4 hour .obs file. With a running gpsd accessible on the localhost do all of the following, in order. Order matters.

The raw measurement messages are long. Be sure your serial port speed is high enough:

    gpsctl -s 115200

Disable all NMEA messages, and enable binary messages:

    ubxtool -d NMEA
    ubxtool -e BINARY

The NEO-M8N will only reliably output raw measurements when only the GPS and QZSS constellations are enabled. If your PPP service can use GLONASS, then enable that as well. Be sure to disable, before enable, so as not to momentarily have too many constellations selected. ubxtool, as recommended by u-blox, enables the QZSS constellation in tandem with GPS. Disable all constellations, except GPS (and QZSS):

    ubxtool -d BEIDOU
    ubxtool -d GALILEO
    ubxtool -d GLONASS
    ubxtool -d SBAS
    ubxtool -e GPS

Verify the constellations enabled:

    ubxtool -p CFG-GNSS

Enable the good stuff, the raw measurement messages:

    ubxtool -e RAWX

Verify raw data messages are being sent:

    ubxtool | fgrep RAWX

You should see this output:

    UBX-RXM-RAWX:
    UBX-RXM-RAWX:

Collect 4 hours of samples at 30 second intervals, save the RINEX observations in the file today.obs:

    gpsrinex -i 30 -n 480 -f today.obs

Wait 4 hours. Enjoy a meal, or do some exercise. When gpsrinex finishes, upload the file today.obs to your favorite PPP service.

Example 2:

Collect raw measurement data from a remote gpsd. Then process it later with gpsrinex and gpsprof.

Ensure the receiver is configured properly, as shown in Example 1.

Grab 4 hours of raw live data from remote gpsd at 10.168.1.2:

    gpspipe -x 14400 -R 10.168.1.2 > 4h-raw.ubx

When gpspipe is complete, the file 4h-raw.ubx will contain 4 hours of raw UBX binary message. Convert that raw data in gpsd JSON with gpsdecode:

    gpsdecode < 4h-raw.ubx > 4h-raw.json

The file 4h-raw.json will now contain the data encoded as gpsd JSON. Use gpsrinex to read that file and create a RINEX file:

    gpsrinex -F 4h-raw.json

The RINEX file will be in the current directory with the file name like: gpsrinexYYYYjjjHHMMSS.obs. See strftime(1) for how the date formatting works

You can now use the JSON file to generate a polar plot of the used satellites:

    gpsprof -f polarused -T jpeg -r < 4h-raw.json > 4h-raw.plot
    gnuplot < 4h-raw.plot > 4h-raw.png

Use the image viewer of your choice to view your skyview in 4h-raw.png

RETURN VALUES

0
    on success.

1
    on failure

SEE ALSO

One service known to work with gbsrinex output is at:

OPUS requires 2 frequency observation files.

The curious can find the RINEX 3.04 format described here:

RINEX 4.02 is here:

gpsd(8), gps(1), gpsprof(1), gpsfake(1). ubxtool(1), gpsd_json(5), strftime(1)

RESOURCES

Project web site:

COPYING

This file is Copyright by the GPSD project
SPDX-License-Identifier: BSD-2-clause

AUTHOR

Gary E. Miller