British Gas Plc

Paul B Cordes

David J Gunton

Roger Philip Ashworth

Richard C Thomas

Michael P Stansfield

Howard F Scott

Stewart M Pegler

A wheeled support assembly 10 is manually pushed over the ground and has a motor 22 rotating an antenna assembly 60 about a vertical axis 24. Encoders 28 on the antenna shaft 20 and on a wheel axle encode antenna angular position and position over the ground. Transmitted pulses and received data pass through a rotary microwave connector 26. For example, 400 sets of pulses are emitted at equal angular intervals in each revolution of the antenna assembly. The interval between pulses is e.g. 12 microseconds, with 256 pulses per set. Noise reduction is achieved by processing the received data accordingly. In a modification the rotary connector 26 is single channel with some electronic stages mounted on the rotating antenna assembly. Power is coupled to them via the microwave cable. An umbilical connects the assembly 10 to a support facility including a computer. Alternatively, battery power is used with data transferred radiatively.

Ground probing radar method and apparatus

A method of detection of inaccessible metallic objects such as gas, electricity, water or telecommunications systems (lines) through which an alternating current is flowing, comprises making at least three spatially separated measurements of the magnetic field associated with the current. Signals derived from the measurements are compared in a detector which gives an output indication when the signals derived from the measurements at the two outer locations are equal and each less than the signal derived from the measurement at the intermediate location. A suitable sensing device has four equally spaced pickup coils and operates at a frequency of 43KHz. The alternating current detected in the metallic objects may be induced by a separate transmitter.

Apparatus and method for detecting the location of metallic objects

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Whitley Bay, United Kingdom

Paul B Cordes