The 3-Space Sensor family of intelligent IMUs and AHRS from YEI Technology, Portsmouth, OH, determine orientation relative to an absolute reference orientation in real time. The devices combine triaxial gyroscopes, triaxial accelerometers, and compass sensors with onboard filtering and processing algorithms and are offered in a range of communication, performance, and packaging options, including an ultraminiature surface-mountable TSS Embedded module, a TSS Wireless 2.4 GHz module, and TSS Data logging versions. Orientation can be returned in absolute terms or relative to a designated reference orientation. Multireference mode increases accuracy and reduces and compensates for sensor error.