Fig. 10From: An overview of behavioral, physiological, and environmental sensors used in animal biotelemetry and biologging studiesExplanation of the light gradient sensor. The most basic bearing sensor design is composed of three parts: a light emitter array, a compass wheel with magnet, and a light detector array (a). A transparency gradient on a disk of negative film shown with the boundary between the most transparent and least transparent wedge (b). The resistance of the two photoresistors are plotted over a directional rose of 360°, with the blue arrows indicating the ambiguity zone for sensor #1 and red arrows denoting the ambiguity zone for sensor #2 (c). The sensor is shown without its opaque coating to keep out external light. One must be careful to cover the sensor with multiple coasts of a dark epoxy paint and to measure resistances when the room light are off and on to make sure no external light enters the sensorBack to article page