| 摘要 |
An apparatus for determining an elevation of a working tool relative to a reference plane (100) comprises a rotary laser system (110) emitting at least two non-parallel fan-shaped laser beams (120) diverging in a plane inclined relative to the reference plane (100), a radio unit configured to measure a distance (150) between the working tool and the rotary laser system (110) and a detector (130) mounted on the working tool for detecting each of the laser beams. The elevation of the working tool is determined on a basis of a time delay between the receipt of the fan-shaped laser beams (120) at the detector (130) and the distance (150) between the working tool and the rotary laser system (110) .
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