| 摘要 |
An underground marker of ground coil type has been made into a narrow, elongated cylindrical unit, which is easy to fit in a hole without actual excavation work. The unit comprises a resonant circuit with a coil, which is wound on top of a ferrite core, the diameter of the unit being kept small. The unit housing has thick walls in order to guarantee good dielectric characteristics in the immediate surroundings of the coil, regardless of the installation conditions, and the housing is sealed in order to retain the dielectric characteristics of the internal part. The marker is extremely durable and reliable and permits especially accurate locating of the surface point situated above the marker, and in practice this is crucial to the important new application or for use of such markers, that is to say for the use of underground markers to mark official fixed points in geodetic and similar ground registration systems. <IMAGE> |
