Following an earlier post on using GPS under Ubuntu, I have been trying to get PolarNavy working under Ubuntu 12.10. Polar Navy is the only Linux chart navigation software available for Linux. I know people will correct me by quoting OpenCPN, but there are no charts currently legally available for the UK, at least that I could find.

Polar Navy has two components - PolarCOM which communicates with the GPS receiver, and PolarView which displays the actual charts. The two applications can connect together, to show the vessel’s current position.

I had Polar Navy working fine under Ubuntu 12.04 i386, but for some reason I had problems running under Ubuntu 12.10 amd64. The problem was that PolarCOM would simply not display the position, i.e. the Lat and Long. I tried running from the command line, and there were a large number of errors when running PolarCOM, for example:\

menu_proxy_module_load': ./PolarCOM.bin: undefined symbol: menu_proxy_module_load (PolarCOM.bin:4487): Gtk-WARNING **: Failed to load type module: (null)

I eventually fixed that by adding the following to the /opt/polarcom/bin/PolarCOM script:

export UBUNTU_MENUPROXY=0

Sadly PolarCOM was still not working. The GPS Receiver that I use is the BU-353, a terrific piece of hardware that “just works” under Linux. This is the recommended GPS for Polar Navy, which was a happy coincidence. When I plugged in the receiver it was detected as /dev/ttyUSB0, which I noticed had a group “dialout”. I added myself to that group:

$ sudo adduser dialout

I posted a request for help on the Polar Navy forums and they suggested I connect directly to the receiver using screen. I was unsure how to terminate that session, but ended up killing the screen session (Ctrl+Alt+a followed by k to kill). There is probably a better way - feel free to comment below.:

$ screen /dev/ttyUSB0 4800

But doing so just output a load of binary garbage, which I realised (with help from Surrey LUG IRC #surrey on irc.lug.org.uk) meant that the receiver was no longer in NMEA mode. Apparently GPSD automatically reconfigures the receiver to SIRC III binary. I have no idea why this was not a problem in Ubuntu 12.04.

To fix this problem I needed to ensure that GPSD was not running. Unfortunately stopping the service does not seem to terminate the process, so I also had to kill it off:

$ sudo service gpsd stop
$ ps aux | grep gps
$ killall PolarCOM.bin

Next I placed the GPS receiver into NMEA ASCII mode, instead of SIRCIII Binary mode:

$ gpsctl -f -n /dev/ttyUSB0

Lastly, you may also need to configure the serial port, although I did not need to do this:

$ stty -F /dev/ttyUSB0 ispeed 4800

A quick check to see that we are getting ASCII NMEA sentences, showed that it was working perfectly, with easy to read text output from the receiver.

$ screen /dev/ttyUSB0 4800

To prevent GPSD from reconfiguring the receiver again, I then needed to reconfigure it to use read-only mode:

$ sudo dpkg-reconfigure gpsd

And at the point where it requests switches, I added “-b” (Broken Device Safety Mode), otherwise known as read-only mode.

With trepidation I launched PolarCOM, which immediately showed my current position.

I have bought myself a GPS Receiver BU-353. Having plugged in the device into my Debian Wheezy workstation, I wanted to test that it was working.

A quick dmesg | tail showed me that the device has been found and installed correctly (no drivers required).

I then installed the GPS daemon:

$ sudo apt-get install gpsd gpsd-clients
$ sudo dpkg-reconfigure gpsd

This then started the GPS daemon. The next thing to do was get some example output, and the tool for this is gpspipe:

$ gpspipe -w -n 5

Lastly, I thought it would be fun to plot the output onto Google Maps and/or Openstreetmaps:

$ tpv=$(gpspipe -w -n 5 | grep -m 1 TPV | cut -d, -f4,6-8,13)
$ latitude=$(echo $tpv | cut -d, -f3 | cut -d: -f2)
$ longitude=$(echo $tpv | cut -d, -f4 | cut -d: -f2)
$ google_map_url="http://maps.google.com/?q=${longitude},${latitude}&z=${zoom}"
$ osm_map_url="http://www.openstreetmap.org/?mlat=${latitude}&mlon=${longitude}&zoom=${zoom}&layers=M"
$ xdg-open $google_map_url
$ xdg-open $osm_map_url

All worked beautifully.