webcraft
Well-Known Member
I was taught that even using the latitude scale to measure distance, you should take it from a point on the scale near to the latitude you are at because the Earth is not exactly round.
The nautical mile is defined to be the average distance on the Earth's surface represented by one minute of latitude, and is constant A minute of latitude expressed as length on the Earth's surface is not constant, though. At the equator a degree of latitude is something between 20 & 40m less than a minute of latitude near either pole.
However, you would have to be a phenomenally accurate navigator with a very small scale chart for this to make any significant difference, so either I was taught by a pedant or there is something else about the latitude scale on standard charts that I am not aware of.
Anyone know which it is?
(Sorry, I realise this is somewhat irrelevant when we are talking about a chart on the knees and a pair of rulers loosely held together by a screw . . . but probably just as relevant to real everyday navigation).
<font color=blue>Nick</font color=blue>
<A target="_blank" HREF=http://www.bluemoment.com>
</A>
The nautical mile is defined to be the average distance on the Earth's surface represented by one minute of latitude, and is constant A minute of latitude expressed as length on the Earth's surface is not constant, though. At the equator a degree of latitude is something between 20 & 40m less than a minute of latitude near either pole.
However, you would have to be a phenomenally accurate navigator with a very small scale chart for this to make any significant difference, so either I was taught by a pedant or there is something else about the latitude scale on standard charts that I am not aware of.
Anyone know which it is?
(Sorry, I realise this is somewhat irrelevant when we are talking about a chart on the knees and a pair of rulers loosely held together by a screw . . . but probably just as relevant to real everyday navigation).
<font color=blue>Nick</font color=blue>
<A target="_blank" HREF=http://www.bluemoment.com>