Abstract: A locating device equipping a mobile body, comprises an inertial platform, a 3D gyrometer and accelerometer, a calculation unit receiving measurements of the gyrometer and accelerometer a sampling frequency, and means to locate the mobile body, the calculation unit performing: a preliminary step where the mobile body travels a known trajectory, calculation of a coefficient of proportionality between distance actually traveled and raw distance obtained by integrating the time derivative of the acceleration along the trajectory; a following step of free displacement, location of the mobile body by dead-reckoning navigation procedure, being performed by using distance traveled the raw distance corrected by the proportionality coefficient.