Bowditch On Disk

Every boater who has ever run up against a navigational problem to which there is a not a clear answer or whoever wanted to settle a yacht club bar bet has at one time or another looked to Bowditch's American Practical Navigator for the definitive answer. The problem with Bowditch and other tomes on navigation is that sometimes finding the answer can be as frustrating as the problem itself.

The easy way to settle these disputes is on a new CD-ROM from Starpath. Bowditch Plus contains the complete text of Bowditch's The American Practical Navigator, in searchable form, on one CD.

I was helping a friend pick out a radar for his boat and he wanted to know how far away he would be able to see objects. He thought since he was considering a thirty-six mile radar he would be able to see larger objects that far away. I explained to him that it was not just the power of the radar but the height at which it was mounted. The formula for finding the distance to the visible horizon is Distance = 1.17 times the square root of the height of the object (the radar or your eye.) (There is a slight difference between radar horizons and visible horizons, but for most purposes, the amount is negligible.)

We went to the Piloting Tables on the CD-ROM, picked Distance of the Horizon, plugged in the height of the radar antenna (25'), and it calculated that under optimal conditions, the radar would reach out to a usable distance of 5.845 statute miles. My friend is now looking a way to raise the height of the radar dome to get a better view. Unlike the book version, this CD actually computes the distance for you, not only saving time, but also eliminating errors due to mathematical mistakes.

Also included on the CD are all the chart symbols, definitions and abbreviations, US and International, indexed by name and graphical design along with all contact and internet links to all the hydrographic offices worldwide. The whole database is searchable. I looked up the Rule for the proper lights to display if you are aground and the program took me directly to the page with rule and the illustration. The complete Navigation Rules, Rules of the Road, are also included. This is a great reference tool.

You can search for terms and symbols, or you can use the convenient indexes to locate what you need. With more and more boats carrying computers onboard, this a reference tool that will help you find what you need in a hurry. The contents can be run from the CD or loaded on the hard disk. If you have the room, load the Rules of the Road and other modules you think you will, need to your hard disk. This gives you quicker access times and smoother operation.

Boats have limited storage space and this CD removes the need to carry a big reference volume with you. It is easy to use and is great example of technology making a complex subject easier to understand.

Bartender, give my buddy my tab.

What's the problem with electronic navigation?

Almost every boat, from a flats sea grass killer to a megayacht, which leaves the dock now, has some form of electronic navigation. From a handheld gps to full-blown nav systems with twenty-two in touch screens, we all navigate with the greatest of ease nowadays. So what is the problem? We do not think about navigation anymore.

The key word is “think.” Anyone can walk onto a boat, push a few buttons, enter coordinates from a waypoint card or position index and off we go. With enough fuel we can navigate across oceans when some people should not be allowed off the dock. Do we understand what we are seeing when we look at the screen of a plotter? Many people do not.

There are the navigationally challenged among us. Take the case of a friend of mine who is tall ship master. On a break, he took a position as second captain on a 113’ Hatteras, on its way to Nassau in the Bahamas. About an hour off the dock the lead captain confessed to my friend he had no idea on how to get there. My friend took over the navigational duties and kept on eye on things until they got there and then he flew home.

Until fairly recently I was an instructor at a maritime school that trained people how to take the Coast Guard exams for various licenses. I taught the 6 pack through 200 ton courses. With 6 packers you expect a lack of knowledge. Many of them, good captains though they may be, rarely go much further than just out of sight of land. For them navigation is a not a great concern. As you climb the ranks, it becomes a much greater consideration. Just ask the commanders of two, not one but two, nuclear subs that ran aground within months of each other while entering Port Everglades.

I had one student who told me he ran an 85 footer for five years but he might have trouble with the chart work. When I asked him why, he said in all that time they never had a compass on board.

Many captains fail to correlate the fact that chart plotters reproduce actual charts. Raster plotters use a high-resolution photo or scan of an actual chart and use software to move it around and zoom in or out, etc. Vector systems reproduce the chart through a series of crossing lines or vectors, and some chart plotters can use both. (See this quick but clear example of the two here.)I am not going to discuss the relative merits of each here. Study up and see which fits your needs best.

One of the things that bothers me most are people who should know better, but cannot read a chart or navigate using one. Batteries die, electrical systems fail, computers freeze and yet people leave the dock with a complete dependence on electronics with no idea what to do if things go south.

So many captains who came through the classes, even at the upper levels, could not do a simple time, distance, speed computation. An example: Calculate time speed distance. Every captain should own a copy of Chapman’s Piloting, Seamanship and Small Boat Handling. At the very least, go the section on basic navigation and work a problem or two.

In order to use a chart plotter effectively and safely, you have to understand latitude and longitude and know how to read a chart. Your plotter will happily run your boat right over a reef if you YOU do not plot a course around it.

Another thing that can get you into to trouble is using charts and computer chips that have two different WGS survey dates. This can affect dramatically the accuracy of your position fix.  Take look here for an explanation. The offset between ED-50 and WGS-84 will typically be in the order of 100 metres. On charts with Norwegian Datum, the difference between the chart graticule and WGS-84 can reach 4-500 metres. With such a large difference between the graticules, it will be very important that the navigator takes this into consideration. If you want the US version an a longer and better explanation, go here. Especially read about how much the thickness of your pencil lead can put your position off.

Don’t know or care what a “graticule” is? Does not matter. What does matter is that the differences in charts can put you off your position by over 1600 feet. Try that on a night approach to Bimini.
Now, lest you think I’m some kind of Luddite old fogey, I’m not. I love what computers on boats can do. I have taught classes on using the various software packages that are out there. I was even on a development team for a large producer of navigational software. However, as much as I enjoy the ease of use, the convenience and interface available with today’s navigation computers, I do not relinquish control of my boat to them.
Get yourself some charts, even a few for you area of cruising and become familiar with them. Besides, you have to have some place to put your coffee cup.
Remember, it’s pointy end first.