Every point on earth (and presumably, any rotating sphere)can be located using latitude (lines parallel to the equator)and longitude(Great Circles in rotational increments
around the Earth). Is there an ALTITUDE coordinate?
By this I don’t mean measured in feet or meters above sea level, but one measured in degrees, like lat. and long.?
Also:
I know that each degree is subdivided into 60 minutes, and each minute is further divided into 60 seconds.
How big an area is one second latitude by one second longitude?
You can’t express altitude in degrees because there is no angle involved. Longitude is expressed as an angle with respect to the prime meridian and latitude is expressed as an angle wrt the equator. This imaginary “angle” passes from the prime meridian/equator, to the center of the earth, then back out to the location of interest. It would be impossible to measure a radial location (e.g. altitude) this way.
I’d have to do some math before I could answer your next question. Someone will probably beat me to it, though.
A minute of arc is 1 nautical mile. A nautical mile is 1852 meters. 1 second would be 1/60th of that, 30.9 meters. Squared, that would be 955 square meters.
As Strainger said, there is no Altitude coordinate expressed in degrees, but (as you speculated) there are measurements and therefore coordinates based on elevation above mean sea level.
And the area of a second squared will depend on where you are on the globe. Since longitude lines meet at the poles, a squared second has zero area there.
You can so express altitude in degrees–it’s called “elevation.” Astronomers do it all the time. The problem is that there is no fixed reference point as there is with latitude and logitude. Usually, elevation is expressed as being x degrees above the horizon.
1" of latitude equals about 31 meters. 1" of longitude can vary from about 31 meters at the equator down to 0 at the poles.
pldennison, I disagree with what you’re saying, and I think your post is plumb confusing.
Elevation or altitude as in angle above the horizon has nothing to do with altitude, or elevation above sea level.
Perhaps surveyors would refer to the elevation angle of a terrestrial object in degrees above horiziontal (anyone who has some more solid info on this should set me straight), but astronomers, amateur or professional, only use elevation angle to describe the position of celestial objects.
You’re right, Podkayne, although the OP specifically said, “By this I don’t mean measured in feet or meters above sea level, but one measured in degrees, like lat. and long.?” I guess that threw me off.
The problem with angular measurements like these are that they always need a reference point. Longitude is measured relative to the Prime Meridian - if you were mapping Mars (or a tennis ball), you would have to create a Prime Meridian based on a geographic feature (not too easy on a tennis ball). Latitude is based on the equator, which is fine for a rotating object, but not much use otherwise - it just becomes another arbitrary line, at right angles to the Prime Meridian arbitrary line. And surveyors are able to measure the elevation of a point by the angle from two or more points - but only from points the locations of which are completely known. This is why the country is full of little bronze survey markers; they mark a point on the earth where the latitude, longitude and elevation are known.
I figured there would be two points you could start out with:
the geometric center of the sphere ( altitude 0 degrees, or -90 degrees)
and any point on the surface (alt POSITIVE 90 degrees or
0 deg)
and continue degrees in altitude out to infinity
You could, but you’d be creating a unit of linear measure and calling it a “degree” (which is a unit of angular measure) - and that would be a source of confusion similar to people who use “light year” as a unit of time. Angular measurement already has enough confusion with “minutes” and “seconds” being used for time measurement as well as angles. We don’t really need further sources of misinterpretation.
Not exactly. You can measure in square degrees, minutes, seconds, etc., using a perfect sphere as a model, and basing the unit on a great circle – any great circle – on that sphere. The area of a sphere is 41,000 “square degrees” and change.
Long story short, it’s a great bloody mess. To insure that your measurement can be meaningfully compared to others, when giving altitude above sea level, you must also cite the sea level measurement you have referred your measurement to.
Just going over some old posts of mine and I think I’ve formulated a geometrically consistent way of expressing altitude in degrees.
Start with a sphere and describe a plane transversing the equator with the sphere’s center as the origin.
Draw a ray (a line with one endpoint and the other end going to infinity) from the “north pole”, i.e. +90 deg., and have the ray pass through the plane to connect with -89deg,-88deg,-87deg, etc. up to 0 deg., on the equator. On the plane, this would describe negative altitude degrees within the volume of the sphere, and 0 degrees as the sphere’s surface.
Continuing this ray tracing (now transversing the positive latitudes before connecting with the plane) will continue marking off degrees on the plane up to +90 degrees, which would be a ray paralel to the plane and thus infinitely away from the origin.
Roughly stated, 0 degrees alt=sea level; -45deg= somewhere in the mantle; and +20deg= somewhere in orbit.
