circle of equal altitude

circle of equal altitude

[′sər·kəl əv ′ē·kwəl ′al·tə‚tüd] (geodesy) A circle on the surface of the earth, on every point of which the altitude of a given celestial body is the same at a given instant; the pole of this circle is the geographical position of the body, and the great-circle distance from this pole to the circle is the zenith distance of the body.

circle of equal altitude

A circle on the surface of the earth, having as its center the substellar points of a given celestial body, from any point on or above the circumference of which the angular altitude of the body is the same. Also called a circle of position.