gnomonautical

Gnomonautical is a term that describes the practice or study of navigation using a gnomon. A gnomon is the part of a sundial that casts a shadow. Historically, and in some specialized contexts, the position and movement of this shadow could be used to determine latitude and, by extension, aid in navigation.

The fundamental principle behind gnomonautical navigation relies on the fact that the sun's apparent position in the sky varies predictably with latitude and time of day. By observing the length and direction of the gnomon's shadow at solar noon, one could calculate their latitude. This method was particularly important before the widespread availability of more sophisticated navigational instruments like the sextant or chronometer.

While not a primary method of modern navigation, the concept of gnomonautical observation is still relevant in understanding historical navigational techniques and in certain niche applications. It highlights the ingenuity of early astronomers and navigators in using the celestial bodies and simple tools to understand their position on Earth. The term itself is a portmanteau, combining "gnomon" with "nautical," referencing seafaring or navigation.