Method and system for mapping a subsurface target region

A system for mapping a target region of a volume below an upper soil surface that comprises a plurality of portions with signal scatterers, the system comprising a processing device configured to:

• acquire a copy of a probing signal from a signal transmitter that has transmitted the probing signal towards the target region;
• acquire a copy of a response signal from a signal receiver, the response signal being a composition of a plurality of signal components that result from scattering of the probing signal by respective ones of the plurality of portions of the target region;
• acquire location and timing data from the signal transmitter and/or receiver representing instantaneous positions of the signal transmitter and/or receiver repeatedly determined during transmitting and receiving;
• wherein the signal transmitter defines a transmitter soil distance with the upper soil surface of less than about meters, and wherein the signal receiver defines a receiver soil distance with the upper soil surface of less than 500 meters;
• wherein a line is defined between the signal transmitter and the signal receiver;
• and
• wherein each of the plurality of portions defines a distance to the line which is larger than the transmitter soil distance and the receiver soil distance,
• transform the copy of the probing signal into a plurality of test signals, each test signal being associated with a signal propagation path via a selected portion of the target region;
• correlate each of the plurality of test signals with the copy of the response signal in a time domain, to calculate a map of correlation strength values associated with respective selected portions of the target region;
• wherein at least one of the signal transmitter and the signal receiver was moving along a respective trajectory relative to the target region while transmitting the probing signal or receiving the response signal respectively;
• and wherein the probing signal comprises a time sequence of noise with a predefined bandwidth, wherein the transforming of the copy of the probing signal for each selected portion of the target region comprises:
• calculating a total delay time based on an effective propagation speed within a signal carrying medium and on a propagation distance from a first instantaneous position of the signal transmitter at a time tT that the probing signal was transmitted, towards the selected portion where the probing signal was scattered, and further towards a second instantaneous position of the signal receiver at a time tR the response signal was received, wherein the determined instantaneous positions comprise the first instantaneous position and the second instantaneous position;
• and
• shifting parts or all of the copy of the probing signal in time, by correcting for the calculated total delay time, to obtain the test signal associated with the selected portion of the target region.