A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: David Iwancio
Date: 2020 Dec 30, 17:25 -0800
I probably haven't read as many texts on the subject as others here, but in triangle PZG where P is the elevated pole, Z the observer's zenith and G the star's geographic point, the conventions in navigational texts I've seen usually refer to the sides as being the complements ("co-X," e.g. "cosine") of values directly published or directly measured. So I've generally seen side PZ named "co-latitude" (or "colatitude") and side ZG as "co-altitude" (I've never seen "coältitude" and thankfully have never seen "coaltitude").
Texts on generalized astronomy tend to call side PZ "zenith distance," probably because land-based astronomers tend to measure angles off their local vertical rather than their horizontal.
Side PG I've generally seen named "polar distance" rather than "co-declination," probably because the declination's complement depends on its name and the name of the elevated pole, and "polar distance" is less ambiguous.