Patent ID: 8791701

Claim:
An electromagnetic proximity detection method for a buried structure executed with a mobile detection device comprising the steps of: sensing an electromagnetic field emitted from the structure as an analog electrical signal; digitalizing the analog electrical signal as a digital signal; filtering the analog and/or digital signal; determining the proximity of the buried structure by analyzing the digital signal; wherein the detecting method can be alternatively executed in at least two of the following modes of detection: a Power-Mode of detection, wherein electromagnetic fields with a fundamental frequency of mains supply are detected; or a Radio-Mode of detection wherein electromagnetic fields in a range of radio frequencies are detected; or an Active-Mode of detection wherein electromagnetic fields with a frequency specified by a known signal being artificially introduced to the structure are detected, further comprising an additional Switching-Mode of operation wherein a repeated sequential detecting in at least two of the Power-Mode of detection, Radio-Mode of detection, and Active-Mode of detection is done by automatic subsequent alternating of the mode of detection, wherein the Power-Mode of detection is detecting the structures only based on higher order harmonics of the fundamental frequency of mains supply and the alternating of the mode of detection is done with such a minimum rate of alternation that an area of detection is coverable by the at least two modes of detection in a single execution of the method; and thereby making multiple structures which emit electromagnetic fields of different frequencies accurately detectable by moving the detection device only once over the area of detection.