Many animals have some kind of ‘home’ –a nest, a burrow, etc. This applies to insects that build nests and provide their larvae with food just as much as to numerous species of vertebrates. Rodents and moles are known to dig burrows; most other mammals, reptiles, amphibians and even many fresh-water fish do not roam around randomly either, but have well-defined home ranges with favourite resting places in particular cavities, under rocks or in dense thickets. Birds build nests for their young and fly out searching for food. All these animals permanently face orientation problems: they have to move swiftly and efficiently within their home range, and they must be capable of returning home when they have left their familiar area while exploring, fleeing, etc.

In 1991 Trimble Navigation introduced a Global Positioning System (Gps)-based attitude determination receiver capable of 3-axis solutions with accuracy to several milliradians for airborne, sea and land platforms. This paper discusses the physical, architectural, and operational features of this receiver system. Analysis of system performance will also be reviewed for various configurations and user applications. The Trimble Navigation attitude determination receiver uses differential carrier phase techniques to determine azimuth, pitch and roll angles of a 3-antenna array. This product is designed to operate in a variety of user applications and to withstand rugged operating environments. Trimble Navigation has expanded its proven GPS sensor architecture to incorporate three independent RF sections and additional processing channels to measure and process the differential phase between antennas on two orthogonal baselines. Direct measurement of differential phase utilizing a common local oscillator provides highly accurate relative phase data. The navigation and attitude processor computes azimuth, pitch, and roll angles as well as position, velocity and time. The solution accuracy and stability statistics are sensitive to various parameters. Antenna baseline length, signal multipath, platform dynamics and filtering are investigated. Test data from static and various dynamic platforms are also presented.