gpssubframe - tool to dump subframe sentences from gpsd


gpssubframe [OPTIONS] [server[:port[:device]]]

gpssubframe -h

gpssubframe -V


gpssubframe is a tool to connect to gpsd and dump decoded subframe data to stdout. This is only useful if your GNSS receiver can output GPS subframe messages, and is configured to do so. A working knowledge of IS-GPS-200 is also required. Keep your copy close at hand.

gpssubframe does not require root privileges, but will run fine as root. It can be run concurrently with other tools connecting to the local gpsd without causing problems.

The program will accumulate subframe messages and output them by GPS satellite number on exit. By default the program never exits unless the user selects the number of seconds to run or number of messages to capture.

By default gpssubframe connects to a gpsd running on the local host. Optionally a host, TCP/IP port number and remote device can be given.


-?, -h, --help

-Print a usage message and exit.

-c COUNT, --count COUNT

Exit after COUNT subframe messages.

-D DEBUG, --debug DEBUG

Set level of debug. Must be integer. Default 0.


Print long descriptions.

--device DEVICE

Connect to device DEVICE on gpsd host.

-D LVL, --debug LVL

Set debug level to LVL.

--file FILE

Read gpsd JSON from FILE instead of from gpsd..

--host HOST

Connect to gpsd on host HOST.


Load saved JSON Subframe, TPV, and RAW data trom LOADFILE.

-n COUNT, --count COUNT

Count of messages to parse. 0 to disable.

--port PORT

Connect to gpsd on port PORT.


Print progress reports as messages are received.


Compute GPS satellite positions before exit. If --time is given, the positions will be calculated at the time. Otherwise if a RAW message was received, the measurement time in that message will be used. The last resort is to use the time from the last TPV message is used.


Save decoded Subframe data in SAVEFILE as JSON. If present, the last TPV and RAW JSON records will also be saved.


Run --satpos selftest code.

--time SEC

Compute satellite position at time SEC in POSIX seconds.

-V, --version

Print the program version, then exit.

-x SEC, --seconds SEC

Seconds of messages to parse. 0 to disable.


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


First configure a u-blox 9-series to output subframe messages. Then have gpssubframe gather one complete set of subframes, then print the data organized by GPS satellite number. Be sure to replace -P 22 with the correct protocol version for your receiver. Then calculate and print the known satellite positions as well as the azimuth, elevation, and range from the current position:

ubxtool -P 22 -e SFRBX
gpssubframe -x 750 --satpos

If staring at a blank screen for 12.5 minutes is too stressful, then enable progress messages:

gpssubframe -x 750 --satpos --progress



on success.


on failure


gpsd(8), gps(1), gpsprof(1), gpsfake(1).

IS-GPS-200 "NAVSTAR GPS Space Segment/Navigation User Segment Interfaces"


Project web site:


This file is Copyright 2020 by the GPSD project
SPDX-License-Identifier: BSD-2-clause