What is geolocation?

Geolocation is the process by which we infer the geographic positions of a tagged individual from the data recorded from an archival tag when direct positioning is not possible (e.g. GPS and other satellite systems). Geolocation can be performed in a variety of ways, depending on the available recorded data streams. Data used to geolocation include, but are not limited to, light for animals spending a significant amount of time near the surface, depth/ tidal variations, and magnetic field signal for deep-diving and demersal animals.

Light-based geolocation

Light is one of the most commonly collected data streams in electronic tags when positioning is required. When used in combination with a reliable clock, light can be fairly reliable in providing the time of local, which in turn can be calculated via standard astronomical equations into longitude. Latitude can also be calculated from light data based on day length, or estimated from temperature or magnetic field signals based on a given, estimated longitude. Light-estimated latitude is most unreliable around the times of equinoxes (March 22, September 23) when everywhere on the planet has approximately 12 hours of daylight.