gpsd.1

很好的一个gps daemon驱动,简单实用

.\"Generated by db2man.xsl. Don't modify this, modify the source.
.de Sh \" Subsection
.br
.if t .Sp
.ne 5
.PP
\fB\\$1\fR
.PP
..
.de Sp \" Vertical space (when we can't use .PP)
.if t .sp .5v
.if n .sp
..
.de Ip \" List item
.br
.ie \\n(.$>=3 .ne \\$3
.el .ne 3
.IP "\\$1" \\$2
..
.TH "GPSD" 1 "" "" ""
.SH NAME
gpsd, gps, xgpsspeed \- interface daemon for GPS receivers, test client, and speedometer
.SH "SYNOPSIS"
.ad l
.hy 0
.HP 5
\fBgpsd\fR [\-T\ \fIGPS\-type\fR] [\-p\ \fIGPS\-devicename\fR] [\-S\ \fIlistener\-port\fR] [\-s\ \fIbaudrate\fR] [\-d\ \fIDGPS\-server\fR] [\-i\ \fIinitial\-position\fR] [\-n] [\-h] [\-D\ \fIdebuglevel\fR]
.ad
.hy
.ad l
.hy 0
.HP 4
\fBgps\fR [\fIX\-options\fR] [\-h] [\fIserver\fR]
.ad
.hy
.ad l
.hy 0
.HP 10
\fBxgpsspeed\fR [\-rv] [\-nc\ \fIX\-color\fR] [\-h] [\fIserver\fR]
.ad
.hy

.SH "DESCRIPTION"

.SS "gpsd"

.PP
gpsd is a monitor daemon that watches a TCP/IP port (2947 by default), waiting for an application to request location information from a GPS\&. The GPS is expected to be direct\-connected to the machine running gpsd via a USB or RS232C serial port which is specified to gpsd at startup\&.

.PP
Optionally, gpsd may get differential\-GPS corrections from a ground station running a RTCM\-S104 server; this will improve position\-fix accuracy from roughly 10 meters to roughly 2 meters, provided you are within 1000 kilometers or so of the ground station\&.

.PP
The program accepts the following options:

.TP
\-p
Set GPS device name (default is \fI/dev/gps\fR)\&.

.TP
\-T \fIdevice\-type\fR
Set GPS type, usually not necessary because most GPSes now speak the standard NMEA 0183 protocol\&. For a list of driver types, look at what \fBgpsd \-?\fR writes to standard output\&. This option may be unavailable if the daemon was compiled without support for the non\-NMEA drivers\&.

.TP
\-S
Set TCP/IP port (default is 2947)\&.

.TP
\-s
Set GPS communication speed in bits per second (default is set by device type)\&.

.TP
\-d
Query a differential\-GPS (DGPS) server\&. If a suffix of the server name begins with ":" it is interpreted as a port number, overriding the default IANA\-assigned port of 2101\&. For DGPS servers available for use with this option, see DGPS corrections over the Internet: \fIhttp://www.wsrcc.com/wolfgang/gps/dgps-ip.html\fR\&.

.TP
\-i
Set initial longitude/latitude in degrees (TripMate and EarthMate only; helps them develop a first fix more quickly)\&. Required format is %f[NS]:%f[EW]; that is a decimal number of degrees latitude, followed by the suffix N or S, followed by a colon, followed by a decimal number of degrees longitude, followed by the suffix E or W\&. The numbers may have fractional parts to the right of a decimal point\&. This option may be unavailable if the daemon was compiled without TripMate or EarthMate support\&.

.TP
\-n
Don't wait for a client to connect before polling the GPS\&. The wait is a feature; many serial GPSes go to a standby mode (not drawing power) before the host machine asserts DTR, so waiting for the first actual request can save valuable battery power on portable equipment\&. This option combines well with \-D2 to enable monitoring of the GPS data stream\&.

.TP
\-h
Display help message and terminate\&.

.TP
\-D
Set debug level\&. At debug levels 2 and above, gpsd stays in foreground and reports incoming sentence and actions to standard error\&.

.PP
gpsd should be able to query any GPS that speaks either the standard textual NMEA 0183 protocol or the binary Rockwell protocol used by EarthMate and some other GPSes\&.

.PP
The request protocol for gpsd clients is very simple\&. Each request consists of a single ASCII character followed by a newline\&. Case of the request character is ignored, Each request returns a line of response text ended by a CR/LF\&. Requests and responses are as follows, with %f standing for a decimal float numeral and %d for decimal integer numeral:

.TP
a
The current altitude as "A=%f", meters above mean sea level\&.

.TP
d
Returns the UTC time in the ISO 8601 format, "D=yyyy\-mm\-ddThh:nmm:ss\&.ssZ"\&. Digits of precision in the fractional\-seconds part will vary and may be zero\&.

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

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

.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": a count of satellites used in the last fix, and three estimated position errors in meters -- position, horizontal, and vertical\&.

.TP
r
Sets or toggles 'raw' mode\&. Return "R=0" or "R=1"\&. In raw mode you read the NMEA data stream from the GPS\&. (Non\-NMEA GPSes get their communication format translated to NMEA on the fly\&.) The command 'r' immediately followed by the digit '1' or the plus sign '+' sets raw mode\&. The command 'r' followed by the digit '0' or the minus sign '\-' clears raw mode\&. The command 'r' with neither suffix toggles raw mode\&.

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

.TP
w
Sets or toggles 'watcher' mode (see the descroiption 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=1" if the GPS is online, "X=0" if not\&.

.TP
y
Returns Y= followed by 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\&.

.PP
Note that a response consisting of just ? following the = means that there is no valid data available\&.

.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 the GPS repeatedly unplugged and plugged back in\&.

.PP
The recommended mode for clients is watcher mode\&. In watcher mode gpsd ships a line of data to the client each time the the GPS sends a sentence, but rather than being raw NMEA the line is a gpsd response as if the user had just sent some set of gpsd commands\&. That set of commands is the minimum for which the incoming sentence is relevant -- e\&.g\&., a GPRMC sentence ships a "pvs" response because it contains position, velocity and GPS status data\&. Additionally, watching clients get notifications in the form X=0 or X=1 when the online/offline status of the GPS changes\&.

.PP
Sending SIGHUP to a running gpsd forces it to close the GPS and all client connections\&. It will then attempt to reconnect to the GPS and resume listening for client connections\&. This may be useful if your GPS enters a wedged or confused state but can be soft\-reset by pulling down DTR\&.

.SS "gps"

.PP
gps is a simple test client for gpsd with an X interface\&. It displays current GPS animation and (for GPSes that support the feature) the locations of accessible satellites\&.

.PP
gps accepts an \-h option as for gpsd\&. An optional argument may specify an server to get data from; a colon\-separated suffix is taken as a port number\&. The misfeature of previous versions that allowed it to direct\-connect to the serial device has been removed\&.

.SS "xgpsspeed"

.PP
xgpsspeed is a speedometer that uses position information from the GPS\&. It accepts an \-h option and optional argument as for gps\&. Additionally, it accepts \-rv (reverse video) and \-nc (needle color) options\&. The misfeature of previous version that allowed it to direct\-connect to the serial device has been removed\&.

.SH "LIMITATIONS"

.PP
There is a limitation in the accuracy of gpsd\-using applications that stems from the fact that gpsd waits passively for updates from the sensor rather than actively polling for them (which can't be done in a device\-independent way)\&. Most GPSes ship updates just once per second\&. At 50km/h (31mi/h) that's 13\&.8 meters change in position between updates\&. This is good enough if you're on foot or in a car but not good enough for aviation applications\&.

.SH "APPLICABLE STANDARDS"

.PP
The official NMEA protocol standard is available on paper from the National Marine Electronics Association: \fIhttp://www.nmea.org/pub/0183/\fR\&. A description of the protocol is available on the Web: \fIhttp://vancouver-webpages.com/peter/nmeafaq.txt\fR\&. gpsd parses the following NMEA sentences: GPRMC, GPGLL, GPVTG, GPGGA, GPGSA, GPGSV\&. Note that gpsd returns pure decimal degrees, not the hybrid degree/minute format described in the NMEA standard\&.

.PP
The Rockwell protocol is described as an addendum on this page about NMEA: \fIhttp://www.gpsinformation.net/dale/nmea.htm\fR\&.

.SH "SEE ALSO"

.PP
 \fBlibgps\fR(3)  \fBlibgpsd\fR(3)  \fBgpsprobe\fR(1) 

.SH "AUTHORS"

.PP
Remco Treffcorn, Derrick Brashear, Russ Nelson, Eric S\&. Raymond\&. This manual page by Eric S\&. Raymond <esr@thyrsus\&.com>\&. There is a project page, with gps screenshots, here: \fIhttp://www.berlios.de/gpsd/\fR\&.