GPS

The Navibe GM720 uses a USB-to-Serial converter from Prolific. The GPS chipset is the SiRF Star III, a recent and famous chipset used in numerous current GPS receivers.

Computer

I use an Apple iBook G4 with Gnu/Linux Gentoo PPC distribution. This 12" iBook is small enough, I can put it in a back bag and the battery allows 3-4 endurance hours.

Hardware ID

lsusb only shows the USB-to-Serial converter:

# lsusb 
Bus 003 Device 002: ID 067b:2303 Prolific Technology, Inc. PL2303 Serial Port

cgps reports: SiRF binary GSW3.2.0PAT_3.

Setting an USB GPS with Linux

A lot of these (all?) USB GPS use the Prolific USB-to-Serial converter. So your kernel needs the pl2303 driver.

Linux kernel setting (here v2.6.23-rc1):

Device Drivers  --->
 [*] USB support  --->
  USB Serial Converter support  --->
   <M> USB Serial Converter support
   <M>   USB Prolific 2303 Single Port Serial Driver

When you plug your USB GPS, you see in /var/log/messages:

Jul 29 17:23:40 iyn usb 3-1: new full speed USB device using ohci_hcd and address 3
Jul 29 17:23:40 iyn usb 3-1: configuration #1 chosen from 1 choice
Jul 29 17:23:40 iyn pl2303 3-1:1.0: pl2303 converter detected
Jul 29 17:23:40 iyn usb 3-1: pl2303 converter now attached to ttyUSB0

If none, verify if the pl2303 module is loaded, with the command lsmod:

# lsmod | grep pl2303
pl2303                 21956  0

If none, the command:

insmod pl2303

loads the module.

You see that the GPS can be accessed with the ttyUSB0 serial device, so I'll use the /dev/ttyUSB0 device name.

Verify you can access your GPS

The gpsd suite has the sirfmon utility which communicates with the GPS through the serial port (or through gpsd, see below).

Starts it with:

sirfmon /dev/ttyUSB0

This software displays on top the informations received from the GPS and on bottom the raw communication with the GPS.

GPSd

The gpsd daemon is an abstraction layer. It communicates through the physical serial port GPS and offers services (lat, long, ...) to its clients (cgps, sirfmon, gpsdrive, navit, ...).

A lot of Linux applications use it, and it is ported to Open/Free/NetBSD and Mac OS X.

It's very simple, just start the daemon with

gpsd /dev/ttyUSB0

If you want to kill it, use the killall gpsd command.

FYI: gpsd installs the usb hotplug rules.

The gpsd suite has a lot of very usefull tools.

Gpsd tools : sirfmon

sirfmon is a SiRF Star III chipset specific tool, it displays a lot of advanced information from this specific chipset class GPS. It'a a textual tool.

Start gpsd if not yet done, and just:

sirfmon

and sirfmon will use gpsd to get geographic informations, see this Sirfmon screenshot:

Gpsd tools : cgps

cgps is also a text tool which displays useful geographic informations, but it isn't specific to one chipset class GPS. See this cgps screenshot:

Gpsd tools : xgps

It's same as cgps but with a graphic interface.

Gpsd tools : cgpxlogger

cgpxlogger is a gps data logger, it displays GPS informations, in GPX format.

Use example:

# cgpxlogger > 2007-07-29_20h08.gpx

and Ctrl-c stop it.

GPX is one of the most known gps data logger format, a lot of applications use it. It's a good solution if you want trace your way or help the OSM project.

GpsDrive

gpsdrive is a car navigation system for laptops. It can download maps from Expedia or TopoZone. See this Gps Drive screenshot:

Navit

navit is a car navigation system for laptops and embedded touch screen displays. For the installation, you need some specific libraries: cegui with openGL support and quesoglc. See this Navit installation page from the project. This is a promising project.

OpenStreetMap

OSM is a collaborative editable map. Most of the current maps have restrictive rights, this project allows each person with a GPS to upgrade the OSM map. Some softwares (like Navit) can use this non-commercial Map. See the current OSM Map.