What is the angle between the horizon and the polar axis called?

The angle between the horizon and the polar axis is called latitude. This is a fundamental concept in geodesy and astronomy, as latitude represents the angular distance of a point on the Earth's surface north or south of the equator. It is measured in degrees, where the equator is 0 degrees latitude, the North Pole is 90 degrees north, and the South Pole is 90 degrees south.

In this context, latitude effectively describes how far a location is from the Earth's equatorial plane, which relates directly to the polar axis. This is critical for understanding geographic coordinates and for navigation, as it helps pinpoint locations on Earth relative to the poles.

Other terms like altitude refer to the angle above the horizon in the sky, while declination is primarily used in celestial navigation to describe the angle of an object relative to the celestial equator. Co-altitude indicates how far an object is from the zenith (the point directly overhead) and is used in different contexts. Therefore, latitude is the term that specifically defines the angle of the polar axis in relation to the horizon at a given location on Earth.