A LOW-POWER POSTPROCESSED DGPS SYSTEM FOR LOGGING THE LOCATIONS OF SHEEP ON HILL PASTURES

Following the explosion at the Chernobyl nuclear plant, airborne cesium-137 was transported into Sweden, the United Kingdom, Iceland, Greenland, and even the northeastern United States. Rainfall washed the radioactive material into the soil, where it was absorbed by the roots of plants. Sheep eating the affected plants threatened to transfer the radiation into the human food chain. Research into the correlation between levels of radioactivity and grass types has led to the need for an instrument that can monitor the positions of sheep at 1 min intervals, with an accuracy of 5 m. An unusual approach to postprocessed differential GPS (DGPS) has been shown to provide the optimal solution to the requirement. The design of the sheep-borne unit has been optimized for minimal power consumption. Furthermore, a low-cost GPS receiver has been shown to serve as a satisfactory reference station, providing the required accuracy without the need for a survey-grade receiver.