Light level geolocator

[2] Also in 1992 was a publication by a different group with a similar design (weight 113g) who called it a global location sensor (GLS) though no field use was mentioned.

[4][5] From albatrosses and other seabirds the use of geolocators has been extended to other migratory species, including waders, wildfowl, raptors and songbirds as designs have become gradually smaller and more energy efficient.

[8] Recording light levels over time produces data that can be used to calculate latitude and longitude readings of a bird's long-distance movements.

The location data so derived is not as accurate as that from GPS or PTT (platform transmitter terminal) tracking involving satellites, but the devices can be made considerably lighter and cheaper.

Other sensors, such as for recording temperature, or whether the logger is wet or dry, may be used in conjunction with the light-level logging in order to provide further ecological information.