device for signalling sousterraine sinalisateur pro ec and for the establishment of fixed points geodesiques or similar marking systems

摘要

A geodetic fixpoint system comprising plural terrestrial fixpoints marked by subterranean fixpoint markers with resonance circuits. The markers reveal themselves by a virtual vertical axis searchable by a surface search detector and the fixpoints are found by intersection between the virtual vertical axis and the ground surface. The markers are mounted with spacing sufficient to allow any fixpoint, when marked visually, to be visible from at least one other fixpoint of the system. The surface search detector generates a frequency which is a nominal resonance frequency of the resonance circuits of the markers, and receives the generated frequency from the markers to search for the virtual vertical axis.