glenda.party
term% ls -F
term% cat index.txt
GPSFS(8)                    System Manager's Manual                   GPSFS(8)



NAME
       gpsfs, gpsevermore - GPS time and position service

SYNOPSIS
       aux/gpsfs [ -d device ] [ -b baud ] [ -s srvname ] [ -m mntpt ]

       aux/gpsevermore [ -d device ] [ -b baud ] [ -n baud ] [ -l location ]

DESCRIPTION
       Aux/gpsfs  reads an NMEA-compatible serial GPS (Global Positioning Sys‐
       tem) device and provides time and position through a  file  system,  by
       default mounted on /mnt and implementing /mnt/gps.

       It  implements  four files in the gps directory: position, time, satel‐
       lites, and raw.

       The read-only position file contains one line of information in 9  tab-
       separated fields:

       fix quality
              0  means  position data invalid, 1 means a 2D position is avail‐
              able, 2 means a 3D position is available.  The value is 8, 9, or
              10,  respectively,  when  the  fix data comes from a file rather
              than an actual GPS.

       zulu time
              universal coordinated time encoded as  hhmmss  followed  by  the
              character 'Z'.

       system time
              time and date converted to the format of time(2).

       longitude
              in degrees, east of Greenwich is positive, west negative.

       latitude
              in degrees, positive is north, negative south of the equator.

       altitude
              above sea level, in meters.

       course degrees, clockwise from true north.

       ground speed
              in km/h

       magnetic deviation
              (not  provided  by  all GPSs), in degrees, positive is westerly,
              negative easterly.

       The read-only time file contains one line of information in 4 tab-sepa‐
       rated fields:

       gps time
              in time(2) format.

       gps time
              in nsec (see time(2)) format (ms accuracy).

       system time
              in  nsec format.  This is the system time at the time of the gps
              time sample.  The difference between this and the previous field
              is used in clock synchronization.  See timesync(8).

       validity
              the  character  A meaning sample valid and usable for clock syn‐
              chronization.  The other values are not usable for clock sync: B
              means  valid  sample from file playback, V means invalid sample,
              and W means invalid playback sample.

       The read-only satellites file contains information  about  the  current
       satellite  constellation.   It consists of one line of general informa‐
       tion, followed by zero or more lines, one for each  satellite  in  use.
       The first line contains two fields:

       fix quality
              same as in the position file.

       satellites in view
              number of satellites above the horizon

       Subsequent lines have four fields:

       prn    satellite ID

       elevation
              above the horizon, degrees.

       azimuth
              direction, degrees from true north

       snr    Signal to noise ratio, 0 - 99 dB

       The  contents of these files are refreshed once per second when reading
       from an actual GPS, and once per 100 ms (giving a speed up of a  factor
       10) when playing back from file.

       The read-only raw file can be read to obtain a copy of the raw NMEA GPS
       output.  Gpsfs keeps an internal buffer of 8KB, so the reader must keep
       up with the output (typically 500 or so bytes per second).

       The  -d  flag establishes the device the GPS samples are read from.  If
       the device file is not a serial interface, gpsfs assumes playback  from
       file and modifies quality parameters as such.

       The  -b  flag specifies the baud rate of the serial line.  The standard
       baud rate for NMEA GPS is 4800 baud, but many device allow changing  to
       higher speeds.

       The  -s flag specifies the name under which the gpsfs service is posted
       in /srv.

       The -m flag specifies a mount mount other than /mnt.

   Evermore
       Aux/gpsevermore is used to configure GPSs using an Evermore chipset.

       The -d flag specifies the serial device to the GPS.

       The -b flag specifies the baud rate of the serial line.   The  standard
       baud  rate for NMEA GPS is 4800 baud, but many device allow changing to
       higher speeds.

       The -n flag specifies the speed to set the GPS to.   When  the  command
       finishes, the GPS should be read (and configured) at the new speed.

       The  -l  flag is sued to specify the location to initialize the GPS to.
       The format is dd:mm:ssX or dd:mm.mmmX or dd.dddX, where dd  stands  for
       degrees (one or more digits), mm for minutes and ss for seconds of arc.
       X is one of W, E, N or S.  Longitudes come with W or E, latitudes  with
       N or S.  The -l flag is followed by two such fields, one for longitude,
       one for latitude.  They may be given in a single argument (separated by
       white  space),  or  in  two arguments, in either order.  Initialization
       time is taken from time(2).

SEE ALSO
       timesync(8), time(2)

FILES
       /mnt/gps/position
              position, time, speed and heading

       /mnt/gps/satellites
              satellites in view

       /mnt/gps/time
              GPS time (millisecond accuracy)

       /dev/eia0
              default GPS device

SOURCE
       /sys/src/cmd/aux/gps



                                                                      GPSFS(8)