Here are the steps for installing GPSD and verifying its performance. They assume you have GPSD available as an installable binary package,

Instructions for building GPSD from source (including cross-building) are in the file "build.txt" in the source distribution.

Most of these installation instructions are generic to Linux (inc There are some special notes on installation for OS X and the Raspberry Pi near the end of this file.

Check that your GPS is live and you can get data from it

Start by making sure you can get data from your GPS, otherwise the later steps will be very frustrating. In this command

stty -F /dev/ttyXXX ispeed 4800 && cat </dev/ttyXXX

replace ttyXXX with the filename of the port. This will probably be either /dev/ttyUSB0 or /dev/ttyS0. If you are on a *BSD Unix or MacOS X, replace -F with -f.

When you run this command, you should see text lines beginning with $ come to stdout (possibly after a short initial burst of binary garbage). If you don’t see this, you may have OS-level problems with your serial support, but more likely have the wrong device. Look again.

If you have trouble with the preceding step, check your cabling first. Verify that the device is connected and that its power LED (if it has one) is lit.

If you seem to have some sort of serial-device problem, check that your kernel properly supports the device you are using. For GPSes using an RS-232 port (which is no longer common) you will need serial-port support compiled into your kernel. Various USB-to-serial adapter chips found in GPSes require specific drivers.

Under a stock Linux kernel these will all be loaded on demand when the USB system sees the appropriate vendor/product ID combinations. See build.txt for instructions relating to custom kernels.

Check that your system configuration will allow GPSD to work

Ensure that device permissions will enable gpsd to read from and write to GPS devices even after it drops root privileges. If you are running Fedora Core, Ubuntu, or stock Debian you can skip this step, as the stock configuration has the right properties.

gpsd requires two things: (1) that GPS devices have group read and write enabled, and (2) all of them have the same group ID as a prototypical device, typically /dev/ttyS0 under Linux or /dev/tty00 under *BSD. It does not actually matter what the owning group is, as gpsd will look this up on startup. Alternatively, (3), you can set a fallback group with the gpsd-group option in case the prototype is not found: this should be the group that has write access to serial devices. On Debian and derivatives including Ubuntu this is "dialout"; on Gentoo/Fedora/openSuse it is "uucp".

Before dropping privileges, gpsd will ensure that it has access to devices given to it on the command line by forcing their group read and write permissions on.

On a Linux with udev, check the files in /etc/udev/permissions.d to ensure that /dev/tty* devices are all created with the same group and with 0660 permissions.

When gpsd drops privileges, its default is to set uid to nobody and group to the owning group of the prototype device (the configure option gpsd-user=foo will cause gpsd to change to foo instead).

If your system has the Linux hotplug facility installed you can skip the permission-setting part; the hotplug scripts will force the permissions for you. You still have to make sure all the tty devices are in the same group.

Check your installation prerequisites

A minimum build of GPSD can run pretty close to the metal; all it absolutely needs is the C runtime support. The test clients and various additional features have additional prerequisites:

pthreads library

support for PPS timekeeping on serial GPSes

DBUS

gpsd will issue DBUS notifications

ncurses

a test client and the GPS monitor depend on this

libtinfo5

shared low-level terminfo library (see below)

libusb-1.0.x or later

better USB device discovery

Qt + qmake

libQgpsmm depends on this

python2.x(x>=6) or 3.y(y>=2)

required for various clients and utilities

python-GI bindings

the test clients xgps and xgpsspeed, need this

Some ncurses packages contain the terminfo library; some break it out separately as libtinfo5 or libtinfo.

Installing gpsd

Install your distributions package(s)

Up-to-date gpsd packages are generally available for Linux distributions including Debian and derivatives (including Ubuntu and Mint), Fedora and derivatives (including CentOS), openSUSE, PCLinuxOS, Mageia, and Slackware. In the embedded space, CeroWRT carries GPSD. The GPSD package in the FreeBSD ports tree is also reliably up to date. Even if your distribution is not on this list, it is quite likely GPSD has already been packaged for it.

Whatever distribution you are running, the name of the core GPSD package containing the service daemon is almost certainly "gpsd". However, many distributions break up GPSD into separate installable packages for the core daemon and clients; you should search your repository index for anything with gpsd as a prefix.

Install from source code

Directions for installing from source are in the file build.txt found in the source distribution.

How to test the software

  1. Start gpsd. You’ll need to give it as an argument a path to a serial or USB port with a GPS attached to it. Your test command should look something like this:

    gpsd -D 5 -N -n /dev/ttyUSB0
  2. Once gpsd is running, telnet to port 2947. You should see a greeting line that’s a JSON object describing GPSD’s version. Now plug in your GPS (or AIS receiver, or RTCM2 receiver).

  3. Type ?WATCH={"enable":true,"json":true}; to start raw and watcher modes. You should see lines beginning with { that are JSON objects representing reports from your GPS; these are reports in GPSD protocol.

  4. Start the xgps or cgps client. Calling it with no arguments should do the right thing. You should see a display panel with position/velocity-time information, and a satellite display. The displays won’t look very interesting until the GPS acquires satellite lock.

  5. Have patience. If you are cold-starting a new GPS, it may take 15-20 minutes after it gets a skyview for it to download an ephemeris and begin delivering fixes.

  6. A FAQ and troubleshooting instructions can be found at the GPSD project site.

Once you have verified correct operation

  1. If you installed from a .deb under Debian or a Debian-derived system, you may need to ‘dpkg-reconfigure -plow gpsd’ to enable the hotplug magic ("Start gpsd automatically").

  2. Check out the list of supported hardware at the Hardware page on the GPSD project’s website. If your GPS isn’t on the list, please send us information to add a new line to the table. Directions are included on that page. We can also use updates of the latest version number known to work with hardware already supported.

  3. GPSD includes a PHP script that you can use to generate a PHP status page for your GPS if you wish. (It may not be in the core package.) It should be manually copied to your HTTP document directory. The first time it’s invoked, it will generate a file called gpsd_config.inc in that directory containing configuration information; edit to taste.

  4. There are other non-essential scripts that may be useful; these are in the contrib/ directory of the source. They may not be available in the packages available from distributions.

For special instructions related to using GPSD for time service, see the GPSD Time Service HOWTO in the distribution or on the web.

Special Notes for OS X Installation

gpsd will build, install and run on OS X. The easiest way to do so is to first install the MacPorts package. Follow their install procedure at: http://www.macports.org/install.php

Then use their port command to install scons, and optionally git if you want to access the development source.

# port install scons
# port install git

While running gpsd, or scons check, you may run out of shared memory segments. If so, you will see this error message:

gpsd:ERROR: shmat failed: Too many open files

By default OS X allows a very small number of shared segments. You can check your allowed maximum number of shared segments, then increase the maximum number, with these commands:

# sysctl kern.sysv.shmseg=8
kern.sysv.shmseg: 32 -> 8
#   sysctl -a  | fgrep shmseg
kern.sysv.shmseg: 8
# sysctl kern.sysv.shmseg=16
kern.sysv.shmseg: 8 -> 16
#   sysctl -a  | fgrep shmseg
kern.sysv.shmseg: 16

If you are using a USB based GPS you will likely need the Prolific PL2303 driver. You can find it here: http://www.prolific.com.tw/US/ShowProduct.aspx?p_id=229&pcid=41

Special Notes for Rasberry Pi Installation

gpsd will build, install and run on the Rasberry Pi (RasPi) and Pi 2 using Debian jessie. Other distributions based on Debian (raspbian, etc) will work fine as well. The gpsd package in Debian Wheezy is known to be flaky, be sure to update to a new version of gpsd from source.

Raspbian

Before compiling gpsd from source, you will need to update your system as root. Switching to the latest raspbian distribution (jessie) is strongly recommended.

# apt-get update
# apt-get dist-upgrade
# rpi-update
# reboot
# apt-get install scons libncurses5-dev python-dev pps-tools
# apt-get install git-core

Git-core is only required to build from a git repository. pps-tools is for testing PPS inputs.

The rest of the installation is just as for any other source based install, as noted in the file build.txt .

Other Debian derivatives (including stock)

Jessie

# apt-get install scons libncurses5-dev python-dev pps-tools
# apt-get install git-core

Git-core is only required to build from a git repository. pps-tools is for testing PPS inputs.

The rest of the installation is just as for any other source based install, as noted in the file build.txt .

Wheezy

Wheezy, being older, requires updating the tools for compiling and testing gpsd:

You need scons at 2.3.0 or higher to build. If your scons is less than 2.3.0 you will need to get a newer scons from wheezy-backport. Partial instructions are detailed here: http://backports.debian.org/Instructions/

Basically you need to add this line to /etc/apt/sources.list:

deb http://http.debian.net/debian wheezy-backports main

Then do another update:

apt-get update

Which may lead you to this error if you lack a full set of debian keys:

W: GPG error: http://http.debian.net wheezy-backports Release: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 8B48AD6246925553

Partial but detailed instructions to fix that are here:

https://wiki.debian.org/SecureApt

Use either of the following code blocks. The first is more robust:

apt-get install debian-archive-keyring
gpg --keyserver pgpkeys.mit.edu --recv 8B48AD6246925553
gpg -a --export 46925553 |  apt-key add -
apt-get update

You can now install scons from the wheezy-backports repository:

apt-get -t wheezy-backports install scons

and other tools:

# apt-get install scons libncurses5-dev python-dev pps-tools
# apt-get install git-core

Git-core is only required to build from a git repository. pps-tools is for testing PPS inputs.

The rest of the installation is just as for any other source based install, as noted in the file build.txt .

Other Raspberry Pi tips

Note: this does not apply to the RasPi3.

Any USB connected GPS that is known to work with gpsd will work fine on the RasPi. No special instructions apply.

A very popular option is to install the AdaFruit Ultimate GPS HAT. With this GPS you also get a good 1PPS signal. This works as any other GPS with gpsd, but there are two things to note. The GPS takes over the serial console: /dev/ttyAMA0. The PPS signal will be on GPIO Pin #4.

Only three specific changes need to be made to make the HAT work. First in the file /boot/cmdline.txt, remove this part "console=ttyAMA0,115200 kgdboc=ttyAMA0,115200)". That frees the serial port from console use so the GPS can use it.

Second you need to tell the boot process to load the pps_gpio module and attach /dev/pps0 to GPIO pin 4. Do that by adding this line to the bottom of /boot/config.txt: dtoverlay=pps-gpio,gpiopin=4

Reboot so those changes take effect.

Run gpsd like this:

~ # gpsd -D 5 -N -n /dev/ttyAMA0/dev/pps0

If you are on the RasPi with gpsd version 3.17, or above, /dev/pps0 can be autodetected. and used for PPS if available.

gpsd 3.17 and up only:

~ # gpsd -D 5 -N -n /dev/ttyAMA0

You can verify gpsd is using the PPS by running ntpshmmon:

~ # ntpshmmon
#      Name   Seen@                Clock                Real               L Prec
sample NTP0 1461619703.641899335 1461619703.445224418 1461619703.000000000 0  -1
sample NTP2 1461619703.642203397 1461619702.999262204 1461619703.000000000 0 -20
sample NTP0 1461619704.142097363 1461619703.445224418 1461619703.000000000 0  -1
sample NTP2 1461619704.142204134 1461619703.999258157 1461619704.000000000 0 -20

If you do not see NTP2 then you misconfigured the pps_gpio driver.

The serial time is provided to ntpd on NTP0, the PPS time is on NTP2, not on NTP1 like described earlier. So your ntp.conf will need to be adjusted from:

# GPS PPS reference (NTP1)
server 127.127.28.1 prefer
fudge 127.127.28.1 refid PPS

To:

# GPS PPS reference (NTP2)
server 127.127.28.2 prefer
fudge 127.127.28.2 refid PPS

Now proceed as for any other operating system to use gpsd.

Warning, the pps_gpio driver in all linux kernels up to the current 3.19 only reports one edge. Be sure to validate that your PPS signal is not offset by the pulse width.

Detailed instructions are available from their web site: https://learn.adafruit.com/adafruit-ultimate-gps-hat-for-raspberry-pi/

You will need to dig deeper to make the PPS work, here is a good reference: http://www.satsignal.eu/ntp/Raspberry-Pi-NTP.html