AntarcticPilot's latest activity
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AntarcticPilot replied to the thread Why do boats use nautical miles and why are they different than normal miles? Couldn't you just convert it to normal miles or km?.No - it's secant (1/cosine). And of course that's only for a spherical earth - it's MUCH nastier taking into account the ellipsoid. -
AntarcticPilot replied to the thread Why do boats use nautical miles and why are they different than normal miles? Couldn't you just convert it to normal miles or km?.Also, on most charts, the scale varies noticeably from north to south of the chart. This is a property of the Mercator projection; scale...
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AntarcticPilot reacted to Refueler's post in the thread Why do boats use nautical miles and why are they different than normal miles? Couldn't you just convert it to normal miles or km? with
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Measured Miles are I am sure you realise are designed to be made in both directions to average out and negate the tide / current flow. -
AntarcticPilot replied to the thread Why do boats use nautical miles and why are they different than normal miles? Couldn't you just convert it to normal miles or km?.Of course - but my work was in mapping and intimate knowledge of datums, projections and the figure of the earth was all part of it. I...
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AntarcticPilot replied to the thread Why do boats use nautical miles and why are they different than normal miles? Couldn't you just convert it to normal miles or km?.The 1 km squares are defined on a map, not on the surface of the earth. The OS uses a transverse Mercator projection, so distance...
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AntarcticPilot replied to the thread Why do boats use nautical miles and why are they different than normal miles? Couldn't you just convert it to normal miles or km?.For nautical use, it is still a minute of arc and changes in length with latitude. 1852m is actually a middle value in the range that it...
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AntarcticPilot replied to the thread Why do boats use nautical miles and why are they different than normal miles? Couldn't you just convert it to normal miles or km?.I think aircraft use the standard international nautical mile, which is defined in metres - 1852m. Technically you are right - a minute...
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AntarcticPilot reacted to Kwik Decision's post in the thread Why do boats use nautical miles and why are they different than normal miles? Couldn't you just convert it to normal miles or km? with Like.
If you're using a Mercator projection chart, which for coastal cruising round the UK is the majority of them, then for accurate nav it...
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AntarcticPilot replied to the thread Why do boats use nautical miles and why are they different than normal miles? Couldn't you just convert it to normal miles or km?.In Antarctica, the two usual projections are Polar Stereographic with a latitude of true scale at 71°S, and Lambert Conformal Conic with...
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AntarcticPilot replied to the thread Why do boats use nautical miles and why are they different than normal miles? Couldn't you just convert it to normal miles or km?.No. Map projections ALWAYS distort distance, so measuring in kilometres simply doesn't make sense. Angular measurement is the only kind...
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AntarcticPilot replied to the thread Why do boats use nautical miles and why are they different than normal miles? Couldn't you just convert it to normal miles or km?.But the exact size of your "1 km square" actually varies significantly east and west of the OS central meridian (2° W)
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AntarcticPilot replied to the thread Why do boats use nautical miles and why are they different than normal miles? Couldn't you just convert it to normal miles or km?.It's not about measuring distance - it's about relating distance run to position. Nautical miles relate directly to position; kilometres...
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AntarcticPilot replied to the thread Why do boats use nautical miles and why are they different than normal miles? Couldn't you just convert it to normal miles or km?.That's the traditional log, as used for centuries! And the name "knot" derives from the knotted line used to trail the log. The idea was...
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AntarcticPilot replied to the thread Why do boats use nautical miles and why are they different than normal miles? Couldn't you just convert it to normal miles or km?.Because knots and Nautical miles are directly relevant to navigation, and kilometres aren't.
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AntarcticPilot replied to the thread Why do boats use nautical miles and why are they different than normal miles? Couldn't you just convert it to normal miles or km?.But unfortunately, "easy" points of the compass are irrational numbers when expressed in radians, being fractions of Pi! I don't think...