Patent ID: 7299058

Claim:
A position calculation method, comprising the steps of: receiving radio signals between a plurality of respective reference stations and a detection-target station by either said plurality of reference stations or said detection-target station, said plurality of reference stations being radio devices whose positions have been already known, said detection-target station being a radio device whose position has been unknown, measuring physical quantities about distances thereby to measure absolute distances or relative distances between said plurality of respective reference stations and said detection-target station, respectively, and calculating position of said detection-target station based on distance-ranging results and positions of said respective reference stations, said distance-ranging results being said respective distances measured, wherein said calculating step comprises the steps of: calculating respective error degradation quantities ΔEi from said respective distance-ranging results Ri and said positions Pi of said respective reference stations, said respective error degradation quantities being quantities of respective errors by which said respective distance-ranging results influence minimum value of square error function to solve the position of said detection-target station, evaluating said respective distance-ranging results based on said respective error degradation quantities, and updating weight-assigning factors Wi about said respective distance-ranging results, and calculating said position P of said detection-target station based on said respective distance-ranging results, said positions of said respective reference stations, and said respective weight-assigning factors updated.