Levelling
Levelling is the job of measuring and correcting the height differences of a surface or a set of points relative to the horizontal plane. This concept, which comes from surveying, is applied in an RV to the vehicle floor: the reference is the horizontal plane, the measured quantity is the angle on two axes, and the means of correction is the leg lengths.
In classical levelling an instrument establishes a horizontal line of sight and the height differences between points are read against that line. In the RV application the direction of gravity takes the place of the line of sight, and the angle produced by the sensor takes the place of the staff reading.
- Reference: gravity. That is why what is measured is not the ground the vehicle is parked on but the absolute angle of the body.
- Measurement: the angle on two axes; multiplied by the body length it gives the difference in millimetres.
- Correction: a new bearing plane is established by extending the four legs to different lengths.
Knowing the concept brings a practical habit: in levelling the measurement is always made against a known reference, and when the reference is disturbed all the results shift systematically. In a levelling system this reference is defined by the tare. If your measurement results are consistently shifting in one direction, question the reference, not the accuracy of the instrument.
The context in which this term is used: RV automatic levelling guide