Radio location with enhanced z-axis determination

Abstract

An enhanced system for calculating the Z-Axis, or relative height or altitude, of a radio beacon. The present invention uses a barometric pressure sensing device co-located with the radio emitter to transmit data representing relative altitude. To further enhance the Z-Axis determination, one or several barometric sensors, located at known heights, are positioned around the city to provide real time barometric data. This real time data is used to form a differential correction factor which is compared to the to the time varying barometric sensor co-located with the radio emitter, thereby yielding Z-Axis accuracies of up to one (1) foot. Since the altitude essentially becomes a 'known', this information can also be used in the least squares fit algorithm to enhance the X and Y determination as well. As an alternative to differential readings from 'known' altitude barometric sensors, the X,Y position of the radio emitter itself, or a check-in by a user, can be used to determine times when the radio emitter is at a known altitude thus providing occasional positions for 'self' correction. Further, a mobile barometric reference, with a known Z-axis, can be purposely brought in proximity of the unknown altitude transmitter by, for example, a search team to provide differential information. Lastly, additional radio techniques are taught to assist a mobile search team.