The compass for navigation
December 30th 2006 07:20
Lake Macquarie navigate with or without a compass
The compass
There is debate about who had the compass first. The Chinese or the Vikings, it doesn’t matter as it was a bit of a poor instrument anyhow. A loadstone floating in a pail of oil with a few notches around the pail marking out different angles and positions to places of interest. Eventually the compass came of age to resemble something like what we have today. It was used just as much on land as at sea. So sailors can’t claim it as their own.
Not only can a compass show direction of travel or direction to be travelled, but it shows the direction from the ship of different objects. If we have a chart with those objects marked on them we can quite positively mark our own accurate position on the chart. It became an earnest job to provide accurately marked charts so navigators could find their way around. In fact with a good chart and elementary tools like a compass anyone with a basic understanding could become a navigator.
The old compasses were not marked in degrees as are the modern compass. The modern boats compass is marked in 360 deg with every 5 deg being visible. Most yachts and power boats can’t navigate to within 1 deg so why bother with it on the compass. Bigger ships with computer steering can however steer to within a ¼ deg. The old compass was first broken into North, South, East, West then North East, North by North East and East by North East and North by North East and so on. The smallest angle usually used was hence 11.25 deg which became a point. So when a ships helmsman is asked to come up 2 points he is being asked to steer into the wind another 22.5 degrees not 2 degrees as many people think.
Navigation is a fascinating subject that combines pure mathematics with shrewd guess work and estimation. This is why it was often looked at as a black art.
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