A short range
radiolocation system and associated methods that allow the location of an item, such as equipment, containers, pallets, vehicles, or personnel, within a defined area. A small, battery powered, self-contained tag is provided to an item to be located. The tag includes a spread-spectrum
transmitter that transmits a spread-spectrum code and identification information. A plurality of receivers positioned about the area receive signals from a transmitting tag. The position of the tag, and hence the item, is located by
triangulation. The
system employs three different
ranging techniques for providing coarse, intermediate, and fine spatial
position resolution. Coarse positioning information is provided by use of direct-sequence code phase transmitted as a spread-spectrum
signal. Intermediate positioning information is provided by the use of a difference
signal transmitted with the direct-sequence spread-spectrum code. Fine positioning information is provided by use of
carrier phase measurements. An
algorithm is employed to combine the three data sets to provide accurate location measurements.