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Abstract

Methods for calibrating an accelerometer without needing to use external assistance signals, such as GNSS signals. The invention is applicable to accelerometers generally—in both GPS navigation devices and other devices. A method of calibrating an accelerometer, the accelerometer having a bias, comprises: rotating the accelerometer, wherein the orientation of the axis of the accelerometer changes with respect to the local gravity vector; collecting accelerometer measurements as the accelerometer is moving; and calculating the bias and/or scale factor; wherein the accelerometer measurements are primarily due to local gravity. Furthermore, some embodiments of the present invention include a self-calibration process—a process that does not engage the user's attention. For example, in a self-calibration process for an accelerometer in a cell phone the moving step may be the movement of the phone out of a user's pocket to hold it up to view the screen.

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First Claim