Enhanced position calculation

DETAILED DESCRIPTION A first object of the invention is to overcome the problems of the prior art discussed above.
The second object is to achieve a position fix accuracy and reliability appropriate for life safety applications.
A third object of the invention is to locate a low Signal-to-Noise Ratio transmission with increased accuracy.
A further object of the invention is to be able to locate a transmitter which is located inside of a multi-story building.
This process may be further aided by the employment of a search team equipped with a mobile reference unit.
A further object of the invention is to remove position fix errors which result from fixed obstacles.
Another object of the invention is to remove errors from mobile obstacles.
This requires either additional receivers or the ability to employ time diversity.
A further object of the invention is to correct drift errors which result from imperfect time references contained within the various system elements as well as to provide a point or points of common synchronization for the computation of Relative Time-of-Arrival readings.
A further object of the invention is to learn the signature of an area or areas frequented by a user to increase the accuracy of a position fix made at a future time in that same location.
A further object of the invention is to provide intelligent averaging or weighting of previous position fixes in order to further enhance the accuracy of the most recent position fix.
Another object of the invention is to provide cues appropriate to guide a search team equipped with a mobile reference unit to find a transmitter of unknown position.
All radio location systems must provide at least two major functions: (1) to accurately determine a first arriving radio signal or to determine some appropriate attribute of a radio signal which can be used to determine a transmitter's position, (2) computational techniques which are appropriate to convert the information gained into useful position fix information which typically includes latitude, longitude and altitude