| 摘要 |
A method and a device for rock-drilling and/or earth boring of a number of drill-holes to a predetermined bottom surface are disclosed in which a reference surface defined by electro-magnetic radiation is generated parallel to the bottom surface, the distance between the reference surface and the point at which drilling is to be initiated is measured in a direction common to all holes, the penetration of the drill-rod into the ground is added to said distance, and drilling is interrupted when the sum indicates that the bottom surface has been reached. |
