Day 47 May 04
There is one desk in the cabin that is dedicated to navigation. (see pictures). There is an old fashioned paper chart on the desk. It may be old fashioned but it has the wonderful merit of not being dependant on electricity. There are three means of generating electricity on the boat the generator that functions when the main engine is running, a supplementary small generator that works independently of the engine and two windmills sited on the top of the A-frame. We have a big bank of batteries that are kept charged at all times.
To work with the paper chart there is also a sextant and with this manual device you can work out your position on the chart. The trouble is the tables for calculating the position from a sextant reading are kept on a computer so we are dependent on electricity for that.
In addition to all this there are two separate hand held GPS devices that work on normal AA batteries and a satellite phone that will give GPS position that also can work on batteries. It is good to have a few backup systems. You really do need to know where you are when at sea.
The main system for navigation is the dedicated computer system that displays a chart of the sea on the screen as well as the position of the boat on the chart. This is connected to the AIS system (Automatic Identification System) which is used by most boats of any size and certainly commercial shipping. These other vessels are displayed on the navigation screen along with the information that tells you how fast they are travelling, what course they are moving on and most importantly, whether we will crash into them! Very handy when the horizon is only about 5 miles away and the closing speed of us and a commercial vessel might be as much as 20 knots. That means we only have 15 minutes to avoid them once we can see them.
The instruments on the navigation desk show our position in latitude and longitude, our speed through the water, our speed over the ground, the true wind speed, the apparent wind speed, the true wind direction, the apparent wind direction, the temperature of the water, the depth of the water, the course we are steering, our actual course over the ground, the state of the main batteries, the barometric pressure and whether it is rising or falling and also the time. There is lots of information to absorb. The forecast of wind speeds for the next three days is on a separate computer.