Mike Slinn



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• Open Source Navigation Software Tease : Recreational Marine Navigation on Towards Customizable Open Source Navigation Software
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• Replacement Spectra Watermaker Filters
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• Long-awaited Raymarine C70 update available
• Dial A Buoy
• Robotic Sailboats to cross the Atlantic

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Practical Sailor

MarNav - Open Source Software

marnav-discuss

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I love my Spectra watermaker, but the filters are really expensive. Today I found a replacement activated charcoal filter. Spectra resells the KX Matrikx Industries brand for $30.50. The filters are nominal 3 micron extruded carbon, 10″ x 2.75″. Filtersfast.com has the same filter (KX Matrikx +10 /2 10-250-190-975) for $8.50.

I just concluded a passage from British Columbia to California. Between Bodega Bay, CA and the Farallon Islands we encountered dozens of large whales: humpback, grey, and many individuals of a much larger species. Here is a video I took of two of these unknown whales. Any idea what they are?

I’ve had problems with timed transmit mode on my Raymarine C70 for years. The v4.29 software update seems to have finally solved the problem. Updated documentation is here.

NOAA has a useful service called Dial A Buoy. Unfortunately, the only phone number listed is 888-701-8992; if anyone knows of a non-800 number, please let me know.

Please, no bad puns about San Francisco and “Dial a Boy”. This is a high class blog.

The Microtransat Challenge will feature seven robotic craft, without crew, competing in a race across the Atlantic Ocean.

This historic transatlantic race will run between September 29 and October 5, 2008 and start at Viana do Castelo, Portugal. The finishing line lies between the Northern tip of St. Lucia and the Southern tip of Martinique in the Caribbean. The USA is fielding up to two teams, and France, Canada and Portugal will each field a team.

The Pinta was designed at Aberystwyth University, Wales, UK. Pinta is expected to sail for three months at a maximum speed of four knots. Its designers hope the Pinta will become the first robot to cross an ocean using only wind power.

According to Pinta designer Mark Neal, “This is the first time anybody has attempted to sail across any ocean with an automated boat. The big issue in robotics at the moment is longevity and flexibility in a complicated environment. Something that can survive for two to three months completely unassisted while doing something interesting is a major challenge. If it does get there I will be seriously cheerful. It will open up all the oceans to environmental monitoring by robots.”

For more information:

• http://blogs.zdnet.com/emergingtech/?p=919
• http://www.aber.ac.uk/compsci/public/research/research-groups/intelligent-robotics.php
• http://www.gamesfather.com/video/Search-Microtransat-updated-1.htm

In a recent blog, I mentioned that I was developing Linux-based open source navigation software for Willow Garage. In the course of doing this, I discovered that CodeWeavers’ CrossOver Linux product allowed Coastal Explorer / Chart Navigator Pro to run in a win2k bottle. That doesn’t mean that NMEA devices work with programs running under Crossover Office - that would require some extra magic. The Willow Garage autonomous vessel project was canceled before I had time to get GPSes working with CE/CNP under Linux. If anyone is interested in adding NMEA 0183 and/or NMEA2000 support to a Windows navigation program running under Linux, contact me to discuss costs.

On another note, I discovered that the OpenEV package that I had been interested in extending into a nautical navigation program was based on older graphics technology, so I started programming a prototype that ran on Linux. Here is a screen shot:

I wrote the software in Python v2.5.2 using PyGTK v2.10, PyCairo v1.4.12 and Glade v3.4.1 for graphics support, running on Ubuntu Linux v7.10. I used GDAL 1.4.2 to read S-57 vector charts, and imported Google Earth KML data and GPX data using LXML. I used an Internet Communication Engine (ICE) bus to access remote instrumentation data.

Having played with the prototype for a while, were I to undertake a similar project in the future, I think I would design a GUI patterned after that of The Gimp (floating toolbox and multiple viewports), and employ a more sophisticated architecture. I’d write code using a mixture of Jython, Java, C and C++ instead of Python. It would be very cool to have a power efficient navigation computer running on Linux … it would be more stable than running on Windows.

Update July 19/08: Some people have responded to this blog posting, and as a result I have created an open source software project and a dedicated discussion group.

marnav-discuss

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I’m working on a NMEA2000 network. Because this system is highly customized, it is set up on a bench for software development and system debugging. In the following picture you can see that an Agilent E3610A DC power supply is providing 11.75 volts DC to the bus, via a yellow cable that ends in a T junction. On one side is a Maretron M000002 NMEA 2000/ USB Gateway, and on the other side is a Maretron WSO1000 weather receiver.

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I’m helping out at Willow Garage on their autonomous boat project. The onboard navigation computer actually drives the boat, and is supervised by an onboard mission planner. I’m working on a rudimentary remote navigation program so mission personnel can give high-level directions to the mission planner. Both the onboard computer and the remote computer run Ubuntu Linux. All high level software is written in Python and will be open sourced. The remote computer receives a copy of the instrument data feed via wireless.

The only customizable navigation software I know of (EC2007 from SevenCs) costs 5 figures and although it runs on many platforms, it is not very extensible and is not open source. What’s more, there are no other decent commercial navigation software packages available for Linux. Happily, I found a really nice open source GIS package that runs on Linux and Windows which can read S-57 charts such as those published by NOAA. The package, called OpenEV, is written in Python and even has a python command line interpreter … most cool! If you want to play with it, get the FWTools download since the Vexcel download is old. All software dependencies are included in the download. OpenEV is not a navigation program, but it is a great start for building one.

This project I’m currently working on will not result in a generally useful program, but OpenEV could be a great start to an open-source marine navigation program. If you are a programmer with time on your hands, read on. If not, but you would like someone to create an open source navigation program, contact me and offer me a lifetime supply of donuts

Here is a screen shot of OpenEV running on Ubuntu Linux with a customized toolbar menu:

This section for salty geeks only

You can download S57 vector chart data from here. After you download and unzip the charts you want, start up OpenEV and load the file with the 000 file type.

OpenEV is written in Python and uses PyGTK, which provides Python bindings for the GTK+ libraries. PyGTK takes care of memory management and type casting.

If you want to try customizing OpenEV, here are few hints:

• The toolbar can be modified by editing xmlConfig/DefaultIconFile.xml; menu icons belong in pics/.
• The menu can be modified by editing xmlConfig/DefaultMenuFile.xml
• Plug-ins must be placed in tools/
• An example plug-in is provided in pymod/toolexample.py

I found it helpful to use IDLE (apt-get install idle) to browse the Python classes. If you write a script and place it in the FWTools directory, you can launch IDLE as follows:

cd "$(dirname $0)"
export PYTHONPATH=pymod:lib:$PYTHONPATH
idle&

Once IDLE is launched, use the File/Path Browser menu item to browse the source. Double-clicking on a file, class or method will display the code.

The syntax for the embedded Python interpreter is defined here.

Gotta get back to work… anyone else interested using OpenEV to create a navigation system?

I recently gave a presentation about the potential for a wave-powered autonomous research vessel at Willow Garage. Unlike some other wave-powered vessels, my proposal attempts to generate electricity from waves.

Titanium is a special metal because it is very strong, very light, and is highly resistant to galvanic corrosion in sea water. Titanium has the highest strength-to-weight ratio of any metal. Unalloyed titanium is 45% lighter than steel, but is at least as strong. Titanium is used to make propeller shafts and rigging, fishing line and divers’ knives, and is non-toxic even in large doses.

Titan Marine Products specializes in manufacturing titanium marine hardware, including hose clamps and through-hulls. Hugh Richards, product manager told me that “Titanium is almost totally passive, from a galvanic point of view. It won’t speed up galvanic corrosion of other metals.”

Richards said that Titan Marine intends to provide titanium replacements for all metallic components found in a boat bilge. Titan Marine’s R&D staff are currently working on seacocks and tailpieces, and hope to bring them to market next year. Because titanium degrades at temperatures approaching 1500-1700 degrees, high temperature applications such as exhaust manifolds and exhaust hoses are not planned.
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