| | United States Patent: 6,498,969 |
 | | The geometrical characteristic stored in the database 16 depends on the inertial sensor 12 used and must enable a theoretical value of the inertial measurement supplied by the sensor 12 to be calculated, in conjunction with the speed of the vehicle. |
 | | The curvature.rho.(s) of a rail track varies only very slowly as a function of the abscissa s within a curve and the measured value y(t) supplied by a yaw rate gyro can therefore be written y(t).apprxeq..rho.(s).V(s) where.rho.(s) is the curvature of the track at the abscissa s and V(s) is the speed of the vehicle. |
 | | Of course, during this journey of the vehicle for instructing the database 16, the speed-measuring means 13 are calibrated and the traveling conditions are chosen so that there is no slip between the wheels and the rails, so that the measured speed and therefore the abscissae of the track obtained are accurate. |
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