gpsd(1)
NAME
gpsd - interface daemon for GPS receivers
SYNOPSIS
gpsd [-f GPS-devicename] [-F control-socket] [-S listener-port] [-d DGPS-service URL] [-n] [-N] [-h] [-P pidfile] [-D debuglevel] [-V] [[GPS-devicename]...]
DESCRIPTION
Arrayer or a Ntrip broadcaster that reports RTCM-S104 data; this will
improve user error by roughly a factor of four. When gpsd opens a
serial device emitting RTCM-104, it automatically recognizes this
and uses the device as a correction source for all connected
GPSes. See the section called "ACCURACY" and the section called
"FILES" for discussion.
The program accepts the following options:
Arrayquery: "p0 0
reply: "GPSD,P=36.000000 123.000000
query: "d0 0
reply: "GPSD,D=2002-11-16T02:45:05.12Z
Arraynect to any GPSes on its device list 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.
GPS DEVICE MANAGEMENT
Arrayarate from the public gpsd service port, and only locally accessible, in order to prevent remote denial-of-service and spoofing
attacks.
ACCURACY
Arraythis lag is due to the fact that GPSes normally emit fixes once
per second, thus expected latency is 0.5sec. On the personal-computer hardware available in 2005, computation lag induced by gpsd
will be negligible, on the order of a millisecond. Nevertheless,
latency can introduce significant errors for vehicles in motion;
at 50km/h (31mi/h) of speed over ground, 1 second of lag corresponds to 13.8 meters change in position between updates.
USE WITH NTP
Arrayserver 127.127.28.0 minpoll 4 maxpoll 4
fudge 127.127.28.0 time1 0.420 refid GPS
Arrayhave previously used ntpd, and other reference clocks appear in
your configuration, there may be a fixed offset between the GPS
clock and other clocks. The gpsd developers would like to receive
information about the offsets observed by users for each type of
receiver. Please send us the output of the "ntpq -p" command and
the make and type of receiver.
USE WITH D-BUS
Arraystill at a pre-1.0 stage, we will not attempt to document this
interface here. Read the gpsd source code to learn more.
SECURITY AND PERMISSIONS ISSUES
Arrayout inactive client connections. Before the client has issued a
command that requests a channel assignment, a short timeout (60
seconds) applies. There is no timeout for clients in watcher or
raw modes; rather, gpsd drops these clients if they fail to read
data long enough for the outbound socket write buffer to fill.
Clients with an assigned device in polling mode are subject to a
longer timeout (15 minutes).
LIMITATIONS
Arrayat the start of its update cycle (which most consumer-grade NMEA
GPSes do not) and it is after 2099, then the century part of the
dates gpsd delivers will be wrong.
FILES
Arrayfied on the command line does not exist.
APPLICABLE STANDARDS
Arrayprefix, or with the II prefix emitted by Seahawk Autohelm marine
navigation systems, or with the IN prefix emitted by some Garmin
units. It recognizes one vendor extension, PGRME. Note that gpsd
returns pure decimal degrees, not the hybrid degree/minute format
described in the NMEA standard.
SEE ALSO
AUTHORS
ArrayThere is a project page [2]here.