Definition:Colatitude

Definition

In a spherical coordinate system, the colatitude $\theta$ of a point is the angle between the polar axis and the radius vector.

Terrestrial Colatitude

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

Let $\phi$ denote the latitude of $J$.

The (terrestrial) colatitude of $J$ is the (spherical) angle $90 \degrees - \phi$, that is:

if $J$ is in the northern hemisphere of Earth, the colatitude is the (spherical) angle $\sphericalangle NOJ$

if $J$ is in the southern hemisphere of Earth, the colatitude is the (spherical) angle $\sphericalangle SOJ$.

Celestial Colatitude

Let $P$ be a point on the celestial sphere.

Let the celestial latitude of $P$ be $\beta$.

The celestial colatitude of $P$ is defined as:

$90 \degrees - \beta$ when $P$ is closer to the north ecliptic pole

$90 \degrees + \beta$ when $P$ is closer to the south ecliptic pole.

Also see

• Results about colatitude can be found here.

Sources

• 1998: David Nelson: The Penguin Dictionary of Mathematics (2nd ed.) ... (previous) ... (next): colatitude: 1.
• 1998: David Nelson: The Penguin Dictionary of Mathematics (2nd ed.) ... (previous) ... (next): spherical coordinate system
• 2008: David Nelson: The Penguin Dictionary of Mathematics (4th ed.) ... (previous) ... (next): colatitude: 1.
• 2008: David Nelson: The Penguin Dictionary of Mathematics (4th ed.) ... (previous) ... (next): spherical coordinate system