초록 ▼

Methods for GPS-assisted determination of location coordinates of a mobile user or selected position on or adjacent to the Earth's surface with improved accuracy. Elevation readings from an altimeter or barometer are integrated with readings of the GPS-determined elevation coordinate for that locati

Methods for GPS-assisted determination of location coordinates of a mobile user or selected position on or adjacent to the Earth's surface with improved accuracy. Elevation readings from an altimeter or barometer are integrated with readings of the GPS-determined elevation coordinate for that location, using Kalman filter techniques, minimum least square techniques, or comparison of certain statistically defined parameters associated with the altimeter and GPS variables, such as the standard deviation of the expected errors in these variables. The resulting elevation coordinate may be a statistical blend or filtered blend of the altimeter value and a GPS-determined value for the elevation coordinate; or this resulting elevation coordinate can be chosen to be one or the other of these values, based upon comparison of time varying statistical parameters corresponding to the altimeter and the GPS.

대표청구항 ▼

[ We claim:] [1.] A method for determination of location coordinates of a selected position on or adjacent to the Earth's surface with improved accuracy, the method comprising the steps of:receiving GPS signals from N selected GPS satellites (N.gtoreq.3) and determining location coordinates (x.sub.g

[ We claim:] [1.] A method for determination of location coordinates of a selected position on or adjacent to the Earth's surface with improved accuracy, the method comprising the steps of:receiving GPS signals from N selected GPS satellites (N.gtoreq.3) and determining location coordinates (x.sub.gps, y.sub.gps, z.sub.gps) of a selected location on or adjacent the Earth's surface, where the coordinate z.sub.gps (t) is an estimate of a true elevation or vertical coordinate A(t) of the selected location relative to a selected vertical reference location at a time t;providing an altimeter reading z.sub.alt (t) that is an estimate of the elevation coordinate A(t) of the selected location relative to the selected vertical reference location at a time t;computing statistically determined estimates .sigma..sub.gps (t) and .sigma..sub.alt (t) of the standard deviations of the variables z.sub.gps (t) and z.sub.alt (t), respectively, for at least one selected time;defining an estimate A.sub.est (t) of the elevation coordinate A(t) of the selected position to be equal to z.sub.gps (t) if the standard deviations .sigma..sub.gps (t) and .sigma..sub.alt (t) satisfy a selected first criterion, defining A.sub.est (t) to be equal to z.sub.alt (t) if the standard deviations .sigma..sub.gps (t) and .sigma..sub.alt (t) satisfy a selected second criterion, and defining A.sub.est (t) to be equal to a value that lies between the value z.sub.gps (t) and the value z.sub.alt (t) if the standard deviations .sigma..sub.gps (t) and .sigma..sub.alt (t) satisfy neither the first criterion nor the second criterion; andcalibrating the altimeter reading z.sub.alt against an accurate value for z.sub.alt at least once at a selected time t=t.sub.cal subsequent to a time at which an altimeter reading is initially taken.