Clearly distance along lines of longitude is constant, latitude, not so much as you change latitude.
Posted on 02/09/2014 12:44:07 PM PST by rawhide
I was a 46 pilot, the two rotors rotate different directions, the Huey had a trim button for setting the pitch attitude.
“My comment went right over your head. And here you are trying to talk to us regular folks about airspeed measurements...”
Apologies to Windflier for lack of clarity.
“Normal” coyly implies that the standard referred to is somehow “normative”, half a step from “to be preferred or aspired to”, both of which are less than half a step from “morally superior.”
Assuming that American/British units of measurement are “better,” thus more moral, requires a more strenuous defense than most conservatives make. Not that they haven’t tried: I’ve watched, listened, and read while conservative pundits and opinion leaders for nearly four decades browbeat their audiences, condemning the metric system. At the end of it all, what they’re really saying amounts to nothing more consequential than “We’re used to our system, handed down to us lo these many generations, by our revered ancestors. Change would be inconvenient.”
That's about right. We also have no compelling need to change it.
Longitude. A nautical mile is a minute of longitude, not latitude.
A minute of latitude is a much shorter distance closer to the poles vs. closer to the equator. A minute of longitude is (a relatively) constant distance. It is constant if you assume a perfect sphere, which the Earth isn’t. But close enough for many purposes.
Uh, no.
Longitude is east-west measurement and the lines of longitude run north-south. Thus, at the North Pole, you could walk 360 degrees of longitude in seconds.
Latitude is north-south measurment and the lines of latitude run east-west. Forgetting about the slight bulge at the equator, the distance from 1 degree north to 2 degrees north is the same as the distance from 88 degrees north to 89 degrees north.
Clearly distance along lines of longitude is constant, latitude, not so much as you change latitude.
That was pretty cool.
:-)
1. I’m a trained navigator.
2. Notice how close those lines of longitude are at the poles. How could 1 degree of longitude be of equal distance world wide?
3. Notice how those lines of latitude are equal distances apart on a globe? That is because they are equal distances apart.
You my friend are confused, because the lines are perpendicular to what they measure.
The issue is moving along the lines. 1 minute at constant longitude is always 1 nm. 1 min of latitude, not so much.
Just post the URL without any other HTML in the post! and FR automagically makes it a link.
Look at a ruler, notice how the marking lines are perpendicular of the distance being measured. This is what is confusing you.
Look at a map of the world. Tell me how far apart 0 degrees longitude is from 180 degrees longitude when you are at 89 degrees latitude north?
Because they are 2 degrees of latitude apart, you will find them to be 120nm distant, bisecting the north pole.
Now go to the equator (0 degrees latitude) and measure how far apart 0 degrees longitude and 180 degrees longitude are (east or west I don’t care). You will find that they as far apart as two points can possibly be on Earth.
Now go to any line of longitude you wish and measure the distance going north-south between any degree of latitude and its adjacent (and parellel) next line of latitude. You will find them to be 60nm apart, no matter where you go on the globe.
But I dare say, I don’t think you believe me, so take a look at http://www.coastalnavigation.com/samples/sec_1/1_pages/1_2.htm
“The distance between degrees of longitude is about 60 nautical miles at the equator. It is less further north or south as the longitude lines converge towards the poles. Degrees of latitude are always 60 nautical miles apart.”
“The issue is moving along the lines. 1 minute at constant longitude is always 1 nm. 1 min of latitude, not so much.”
They are termed “parallels of latitude”, and “meridians of longitude.”
How did we get to this point? Partly Eurocentrism, partly geomechanics, partly mathematics.
The Eurotrash were the most energetic explorers of the modern age. When they began navigating and measuring their immediate neighborhood, they used a coordinate system convenient to their locale on the surface of our planet: 30 to 60 degrees N latitude. Approximately. Nobody (among those who counted) cared much at the time. But when their descendants began nosing about the polar regions, problems arose.
Geomechanically, our planet spins on its north-south axis. So it was convenient to use a radiating component oriented so: longitude.
Mathematically, it has to do with spherical geometry and its incompatibility with plane geometry. No spherical surface can be projected onto a flat surface without introducing distortions. The practical import for geolocating systems and navigation is that no flat map can ever be perfectly accurate.
These defects can be worked around or lived with. But navigators, surveyors, and mapmakers can never completely ignore the fundamental truth that we live in a suboptimal world.
Convenience, moralizing, and “we’ve always done it that way” might be desirable, satisfying, even imperative to forum members, but are ultimately powerless when they brush up against that suboptimality.
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