Definition:Longitude/Terrestrial

From ProofWiki
Jump to navigation Jump to search

Definition

Let $J$ be a point on Earth's surface that is not one of the two poles $N$ and $S$.

Let $\bigcirc NJS$ be a meridian passing through $J$, whose endpoints are by definition $N$ and $S$.

The (terrestrial) longitude of $J$, and of the meridian $\bigcirc NJS$ itself, is the (spherical) angle that $\bigcirc NJS$ makes with the principal meridian $\bigcirc NKS$.


Longitude-Terrestrial.png


If $\bigcirc NJS$ is on the eastern hemisphere, the longitude is defined as longitude $n \degrees$ east, where $n \degrees$ denotes $n$ degrees (of angle), written $n \degrees \, \mathrm E$.

If $\bigcirc NJS$ is on the western hemisphere, the longitude is defined as longitude $n \degrees$ west, written $n \degrees \, \mathrm W$.

If $\bigcirc NJS$ is the principal meridian itself, the longitude is defined as $0 \degrees$ longitude.

If $\bigcirc NJS$ is the other half of the great circle that contains the principal meridian, the longitude is defined as $180 \degrees$ longitude.


Also known as

Terrestrial longitude is usually known in common parlance as just longitude.

However, this term also encompasses other measurements of longitude, for example celestial longitude and galactic longitude.

Hence on $\mathsf{Pr} \infty \mathsf{fWiki}$ the full term terrestrial longitude is preferred, so as to forestall ambiguity, unless the context is clear.


Sometimes you see the (terrestrial) longitude reported as east (or west) from (or of) Greenwich.


Also see

  • Results about terrestrial longitude can be found here.


Linguistic Note on Longitude

When the word longitude is spoken, an extraneous d is often added: long-di-tude.

This is technically incorrect.


Linguistic Note on Greenwich

The place name Greenwich, in the context of the Greenwich meridian, is pronounced something like Gren-itch or Gren-idge.


Sources

Retrieved from "https://proofwiki.org/w/index.php?title=Definition:Longitude/Terrestrial&oldid=694511"