Steam Navigation
October 25th 2006 18:09
How is your navigation? What navigation gear do you carry on board? Are you capable of guestimating your way across the bay, along the coast or across a sea without a GPS and chart plotter? If you have a radar can you plot the speed, course of other vessels with it?
Very early navigators of course had little in the way of navigation instruments at all. A piece of home spun string, tied to a rock to give depth, (still works today), a look at the sun for time, one finger span for three degrees and one hand span for fifteen degrees or one hour. Direction of the wind, tide and current in relation to the known land mass. That is about as simple as it can get.
These days we expect a compass on board and we are to carry a chart of the area we are boating in by law. An electronic depth sounder of fish finder to give depth and perhaps a sextant as well.
Anything electronic on board is subject to damage and corrosion from salt water and the salt laden atmosphere. Anything magnetic is also affected by anything electronic so there is a factor of error. Consider a lightning strike on board. what a pity if you should survive only to find you can't navigate as every thing electronic and magnetic is stuffed.
Quite simply the less room for error the more opportunity of being correct in your navigation. (I am not dismissing electronic navigation which after all is the most accurate and easy form.)
Your chart will have an inherent error as we now realise after doing comparisons with GPS and other sophisticated navigational tools. This error is only around a couple of hundred metres at worst. Something you can easily eye ball.
A depth sounder made up of a big handline with string that is marked each metre for the first twenty metres and then say each five and then each ten metres with a good size lead sinker is ideal if a bit slow to use.
A sextant (I use a plastic Davis model that I bought for $95) is another insrument that has little or no error depending on how well you use it. The Davis model I have comes with directions for use and for coastal passages it is easy. Remember on coastal passages you are in site of land and only need to take bearings of known land objects. Very little mathmatics involved at all. When I use my handheld compass I have to allow for variation qhich is not the case with the sextant.
Once you are familiar with your sextant, then you can start to explore its use for celestial navigation and get yourself into the mathmatics required for this. Or else you can use the tables avaiable which again takes a lot of the work out of it. Your electronic calculator can have battery failure and unless you know how to do triginometry with an abbacus then Norries tables should be for you.
So take another look around your boat and work out what you have on board that will assist you in navigation. And take the opportunity to learn how to use it.
Very early navigators of course had little in the way of navigation instruments at all. A piece of home spun string, tied to a rock to give depth, (still works today), a look at the sun for time, one finger span for three degrees and one hand span for fifteen degrees or one hour. Direction of the wind, tide and current in relation to the known land mass. That is about as simple as it can get.
These days we expect a compass on board and we are to carry a chart of the area we are boating in by law. An electronic depth sounder of fish finder to give depth and perhaps a sextant as well.
Anything electronic on board is subject to damage and corrosion from salt water and the salt laden atmosphere. Anything magnetic is also affected by anything electronic so there is a factor of error. Consider a lightning strike on board. what a pity if you should survive only to find you can't navigate as every thing electronic and magnetic is stuffed.
Quite simply the less room for error the more opportunity of being correct in your navigation. (I am not dismissing electronic navigation which after all is the most accurate and easy form.)
Your chart will have an inherent error as we now realise after doing comparisons with GPS and other sophisticated navigational tools. This error is only around a couple of hundred metres at worst. Something you can easily eye ball.
A depth sounder made up of a big handline with string that is marked each metre for the first twenty metres and then say each five and then each ten metres with a good size lead sinker is ideal if a bit slow to use.
A sextant (I use a plastic Davis model that I bought for $95) is another insrument that has little or no error depending on how well you use it. The Davis model I have comes with directions for use and for coastal passages it is easy. Remember on coastal passages you are in site of land and only need to take bearings of known land objects. Very little mathmatics involved at all. When I use my handheld compass I have to allow for variation qhich is not the case with the sextant.
Once you are familiar with your sextant, then you can start to explore its use for celestial navigation and get yourself into the mathmatics required for this. Or else you can use the tables avaiable which again takes a lot of the work out of it. Your electronic calculator can have battery failure and unless you know how to do triginometry with an abbacus then Norries tables should be for you.
So take another look around your boat and work out what you have on board that will assist you in navigation. And take the opportunity to learn how to use it.
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