A process of the invention analyzes a moving speed using acceleration data by an acceleration sensor and calculates a moving distance of the object. The process removes each of given candidate values of drift components from angular velocity data by a gyro sensor and generates relative azimuths data pieces. Based on the respective relative azimuths data pieces, the process calculates moving directions of the object. Using the moving distance and moving directions calculated, the process creates plural moving loci corresponding to the candidate values of drift components. By comparing the positions of actual starting and end points of moving in a building with the positions of starting and end points of each moving locus, the process evaluates the moving loci and determines an optimal moving locus out of the moving loci, based on the evaluation result.