gpsd.8

gpsd, a popular GPS daemon.

(At protocol level 1, there was no K command\&.)

.TP
l
Returns three fields: a protocol revision number, the gpsd version, and a list of accepted request letters\&.

.TP
m
The NMEA mode as "M=%d"\&. 0=no mode value yet seen, 1=no fix, 2=2D (no altitude), 3=3D (with altitude)\&.

.TP
n
Get or set the GPS driver mode\&. Without argument, reports the mode as "N=%d"; N=0 means NMEA mode and N=1 means alternate mode (binary if it has one, for SiRF and Evermore chipsets in particular)\&. With argument, set the mode if possible; the new mode will be reported in the response\&. The "N=" form is rejected if more than one client is attached to the channel\&.

.TP
o
Attempts to return a complete time/position/velocity report as a unit\&. Any field for which data is not available being reported as ?\&. If there is no fix, the response is simply "O=?", otherwise a tag and timestamp are always reported\&. Fields are as follows, in order:

.RS

.TP
tag
A tag identifying the last sentence received\&. For NMEA devices this is just the NMEA sentence name; the talker\-ID portion may be useful for distinguishing among results produced by different NMEA talkers in the same wire\&.

.TP
timestamp
Seconds since the Unix epoch, UTC\&. May have a fractional part of up to \&.01sec precision\&.

.TP
time error
Estimated timestamp error (%f, seconds, 95% confidence)\&.

.TP
latitude
Latitude as in the P report (%f, degrees)\&.

.TP
longitude
Longitude as in the P report (%f, degrees)\&.

.TP
altitude
Altitude as in the A report (%f, meters)\&. If the mode field is not 3 this is an estimate and should be treated as unreliable\&.

.TP
horizontal error estimate
Horizontal error estimate as in the E report (%f, meters)\&.

.TP
vertical error estimate
Vertical error estimate as in the E report (%f, meters)\&.

.TP
course over ground
Track as in the T report (%f, degrees)\&.

.TP
speed over ground
Speed (%f, meters/sec)\&. Note: older versions of the O command reported this field in knots\&.

.TP
climb/sink
Vertical velocity as in the U report (%f, meters/sec)\&.

.TP
estimated error in course over ground
Error estimate for course (%f, degrees, 95% confidence)\&.

.TP
estimated error in speed over ground
Error estimate for speed (%f, meters/sec, 95% confidence)\&. Note: older experimental versions of the O command reported this field in knots\&.

.TP
estimated error in climb/sink
Estimated error for climb/sink (%f, meters/sec, 95% confidence)\&.

.TP
mode
The NMEA mode (%d, ?=no mode value yet seen, 1=no fix, 2=2D, 3=3D)\&. (This field was not reported at protocol levels 2 and lower\&.)

.RE
.IP

.TP
p
Returns the current position in the form "P=%f %f"; numbers are in degrees, latitude first\&.

.TP
q
Returns "Q=%d %f %f %f %f %f": a count of satellites used in the last fix, and five dimensionless dilution\-of\-precision (DOP) numbers -- spherical, horizontal, vertical, time, and total geometric\&. These are computed from the satellite geometry; they are factors by which to multiply the estimated UERE (user error in meters at specified confidence level due to ionospheric delay, multipath reception, etc\&.) to get actual circular error ranges in meters (or seconds) at the same confidence level\&. See also the 'e' command\&. Note: Some GPSes may fail to report these, or report only one of them (often HDOP); a value of 0\&.0 should be taken as an indication that the data is not available\&.

Note: Older versions of gpsd reported only the first three DOP numbers, omitting time DOP and total DOP\&.

.TP
r
Sets or toggles 'raw' mode\&. Return "R=0" or "R=1" or "R=2"\&. In raw mode you read the NMEA data stream from each GPS\&. (Non\-NMEA GPSes get their communication format translated to NMEA on the fly\&.) If the device is a source of RTCM\-104 corrections, the corrections are dumped in the textual format described in \fBrtcm104\fR(5)\&.

The command 'r' immediately followed by the digit '1' or the plus sign '+' sets raw mode\&. The command 'r' immediately followed by the digit '2' sets super\-raw mode; for non\-NMEA (binary) GPSes or RTCM\-104 sources this dumps the raw binary packet\&. The command 'r' followed by the digit '0' or the minus sign '\-' clears raw mode\&. The command 'r' with neither suffix toggles raw mode\&.

Note: older versions of gpsd did not support super\-raw mode\&.

.TP
s
The NMEA status as "S=%d"\&. 0=no fix, 1=fix, 2=DGPS\-corrected fix\&.

.TP
t
Track made good; course "T=%f" in degrees from true north\&.

.TP
u
Current rate of climb as "U=%f" in meters per second\&. Some GPSes (not SiRF\-based) do not report this, in that case gpsd computes it using the altitude from the last fix (if available)\&.

.TP
v
The current speed over ground as "V=%f" in knots\&.

.TP
w
Sets or toggles 'watcher' mode (see the description below)\&. Return "W=0" or "W=1"\&.The command 'w' immediately followed by the digit '1' or the plus sign '+' sets watcher mode\&. The command 'w' followed by the digit '0' or the minus sign '\-' clears watcher mode\&. The command 'w' with neither suffix toggles watcher mode\&.

.TP
x
Returns "X=0" if the GPS is offline, "X=%f" if online; in the latter case, %f is a timestamp from when the last sentence was received\&.

(At protocol level 1, the nonzero response was always 1\&.)

.TP
y
Returns Y=, followed by a sentence tag, followed by a timestamp (seconds since the Unix epoch, UTC) and a count not more than 12, followed by that many quintuples of satellite PRNs, elevation/azimuth pairs (elevation an integer formatted as %d in range 0\-90, azimuth an integer formatted as %d in range 0\-359), signal strengths in decibels, and 1 or 0 according as the satellite was or was not used in the last fix\&. Each number is followed by one space\&.

(At protocol level 1, this response had no tag or timestamp\&.)

.TP
z
The Z command returns daemon profiling information of interest to gpsd developers\&. The format of this string is subject to change without notice\&.

.TP
$
The $ command returns daemon profiling information of interest to gpsd developers\&. The format of this string is subject to change without notice\&.

.PP
Note that a response consisting of just ? following the = means that there is no valid data available\&. This may mean either that the device being queried is offline, or (for position/velocity/time queries) that it is online but has no fix\&.

.PP
Requests can be concatenated and sent as a string; gpsd will then respond with a comma\-separated list of replies\&.

.PP
Every gpsd reply will start with the string "GPSD" followed by the replies\&. Examples:

.IP

      query:       "p\\n"
      reply:       "GPSD,P=36\&.000000 123\&.000000\\r\\n"

      query:       "d\\n"
      reply:       "GPSD,D=2002\-11\-16T02:45:05\&.12Z\\r\\n"

      query:       "va\\n"
      reply:       "GPSD,V=0\&.000000,A=37\&.900000\\r\\n"

.PP
When clients are active but the GPS is not responding, gpsd will spin trying to open the GPS device once per second\&. Thus, it can be left running in background and survive having a GPS repeatedly unplugged and plugged back in\&. When it is properly installed along with hotplug notifier scripts feeding it device\-add commands, gpsd should require no configuration or user action to find devices\&.