Vehicle speed determination from audio input for dead reckoning determination in a portable navigation device

摘要

A portable navigation device displaying map information and navigation instructions for use in a vehicle is disclosed. The portable navigation device includes a memory, a display for displaying the map information and navigation instructions, and a microphone for inputting sound signals to the portable navigation device. A processor is used for controlling operation of the portable navigation device and for determining the speed of the vehicle. To determine the speed, the processor receives the sound signals input by the microphone, analyzes the sound signals, determines a speed at which the vehicle is moving according to characteristics of the analyzed received sound signals when not receiving Global Positioning System (GPS) signals with the portable navigation device, and estimates a current location of the vehicle based on the determined speed of the vehicle.