Abstract: A method of calculating the position of a moving body includes: detecting a movement direction of the moving body; calculating a velocity vector of the moving body using a detection result of an acceleration sensor installed in the moving body; correcting the velocity vector using the movement direction; and calculating the position of the moving body using the corrected velocity vector.

Abstract: A position calculation method and apparatus are described. The position calculation apparatus may include an inertial measurement unit and be configured to be coupled with at least one sensor unit for detecting a physical event for use in position calculation. The presence of and type sensor unit may identified, and the position processing to be undertaken may depend on this identification.

Abstract: A satellite orbit data compressing method includes: determining a compression method of a parameter value on the basis of a variation tendency of the parameter value in an orbit model approximating a satellite orbit; and calculating a compressed parameter value by reducing a bit sequence representing the parameter value using the determined compression method.

Abstract: A position calculating method includes: calculating a position of a mobile body based on a positioning signal from a positioning satellite; determining the moving condition of the mobile body based on a detection result of a sensor unit including at least one of an acceleration sensor, an angular speed sensor, and an azimuth sensor; changing an error parameter used for a predetermined Kalman filter process according to the determined moving condition; and correcting the calculated position by the Kalman filter process.

Abstract: A method of determining the reliability of long-term predicted orbit data is disclosed. The method includes: analyzing a variation in the accuracy of the time-series predicted positions included in predicted position data by comparing the predicted positions included in the predicted position data, which is acquired by predicting a position of a positioning satellite in a time series, with actual positions of the positioning satellite corresponding to the predicted positions; and determining the reliability in each of the prediction periods of the long-term predicted orbit data including predicted satellite orbits in a plurality of successive prediction periods on the basis of the analysis result.

Abstract: A method of determining the appropriateness of satellite orbit modeling is provided. The method includes calculating values of parameters, that the predetermined model has, on the basis of predicted position data including a first predicted position at a first point of time and a second predicted position at a second point of time of a positioning satellite in time series, calculating a first and a second calculated positions of the positioning satellite derived from the predetermined model by using the values of the parameters; and determining the appropriateness of the predetermined model using the values of the parameters, on the basis of first difference between the first predicted position and the first calculated position, and seconded difference between the second predicted position and the second calculated position. The predetermined model is used when approximating a satellite orbit of the poisoning satellite.