GPSRINEX(1)

NAME
gpsrinex - Read data from gpsd convert to RINEX3 and save to a file.

SYNOPSIS

gpsrinex [-D debuglevel] [-f filename] [-h] [-i interval] [-n count] [-V] [server [:port [:device]]]

DESCRIPTION

gpsrinex is a tool to connect to gpsd and output the received raw measurements as a RINEX 3 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, and can be run concurrently with other tools connecting to a local or remote gpsd without causing problems.

gpsrinex needs the GPS receiver to be sending raw measurements to gpsd. Only a few GPS have this capability. In addition, the gpsd driver for that GPS must support raw mode. Currently only the u-blox driver has this support. Only a few u-blox 8 GPS 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 3 observation file that is ready to be read by your PPP program. The default filename will be in the form: gpsrinexYYYYJJJHHMMSS.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

-D, --debug [debuglevel]
    set debug level to [debuglevel].

-f, --fileout [filename]
    save RINEX into [filename].

-h, --help
    print a usage message and exit.

-i, --interval [interval]
    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]
    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.

--agency [agency]
    agency

--ant_num [number]
    antenna number

--ant_type [type]
    antenna type

--marker_name [name]
    marker name

--marker_type [type]
    marker type

--observer [observer]
    observer

--rec_num [num]
    receiver number

--rec_type [type]
    receiver type

--rec_vers [vers]
    receiver vers

The following options set floating point numbers that are placed in the generated RINEX 3 obs file.

--ant_e [easting]
    antenna easting in meters

--ant_h [height]
    antenna height in meters

--ant_n [northing]
    antenna northing in meters

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 3 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. The process it later with gpsrinex and gpsprof.

Ensure the GPS 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, feed the data to gpsfake:

    gpsfake -1 -P 3000 4h-raw.ubx

In another window, feed the data to gpsrinex. Use -n 10000000 so that all the data from the raw file is used::

    gpsrinex -i 30 -n 1000000 :3000

Repeat the process with gpsfake to send the data to gpsprof.

SEE ALSO

One service known to work with gbsrinex output is at: https://webapp.geod.nrcan.gc.ca/geod/tools-outils/ppp.php

OPUS requires 2 frequency observation files. https://www.ngs.noaa.gov/OPUS/

The curious can find the RINEX 3.04 format described here: ftp://igs.org/pub/data/format/rinex304.pdf

gpsd(8), gpsfake(1), ubxtool(1).

AUTHOR

Gary E. Miller <gem@rellim.com>.