A system, comprising: an array structured to turn about an interrogation region to interrogate a person in the interrogation region with electromagnetic radiation at one or more frequencies in a range of about 200 MHz to about 1 THz to provide corresponding interrogation signals; and characterised in that the system further comprises one or more processors operable to establish data representative of a map of intensity of the electromagnetic radiation returned from the interrogation region and data representative of a map of relative depth of a reflecting surface along the interrogation region, which correspond to a topographical representation determined from the interrogation signals, the map of intensity and the map of relative depth forming respective images, wherein the one or more processors are operable to generate an output as a function of the data by: segmenting each image into a number of portions; performing a Fourier transform on each portion to obtain a spatial frequency representation of each portion; applying an extraction filter to each spatial frequency portion to obtain corresponding extracted features; and processing the extracted features with a neural network to determine the output, wherein the extraction filter is one of a ring-wedge extraction filter, a sector extraction filter, and a ring extraction filter, the system further comprises a second array being structured to turn about the interrogation region to interrogate the person in the interrogation region with electromagnetic radiation at one or more frequencies in the range of about 200MHz to about 1THz wherein the two arrays are spaced apart from each other to define the interrogation region therebetween; and wherein the system further comprises a device responsive to the output, to provide an indication to an operator if the person is suspected of carrying one or more man-made objects. an array structured to turn about an interrogation region to interrogate a person in the interrogation region with electromagnetic radiation at one or more frequencies in a range of about 200 MHz to about 1 THz to provide corresponding interrogation signals; and characterised in that the system further comprises one or more processors operable to establish data representative of a map of intensity of the electromagnetic radiation returned from the interrogation region and data representative of a map of relative depth of a reflecting surface along the interrogation region, which correspond to a topographical representation determined from the interrogation signals, the map of intensity and the map of relative depth forming respective images, wherein the one or more processors are operable to generate an output as a function of the data by: segmenting each image into a number of portions; performing a Fourier transform on each portion to obtain a spatial frequency representation of each portion; applying an extraction filter to each spatial frequency portion to obtain corresponding extracted features; and processing the extracted features with a neural network to determine the output, wherein the extraction filter is one of a ring-wedge extraction filter, a sector extraction filter, and a ring extraction filter, the system further comprises a second array being structured to turn about the interrogation region to interrogate the person in the interrogation region with electromagnetic radiation at one or more frequencies in the range of about 200MHz to about 1THz wherein the two arrays are spaced apart from each other to define the interrogation region therebetween; and wherein the system further comprises a device responsive to the output, to provide an indication to an operator if the person is suspected of carrying one or more man-made objects. segmenting each image into a number of portions; performing a Fourier transform on each portion to obtain a spatial frequency representation of each portion; applying an extraction filter to each spatial frequency portion to obtain corresponding extracted features; and processing the extracted features with a neural network to determine the output, wherein the extraction filter is one of a ring-wedge extraction filter, a sector extraction filter, and a ring extraction filter, the system further comprises a second array being structured to turn about the interrogation region to interrogate the person in the interrogation region with electromagnetic radiation at one or more frequencies in the range of about 200MHz to about 1THz wherein the two arrays are spaced apart from each other to define the interrogation region therebetween; and wherein the system further comprises a device responsive to the output, to provide an indication to an operator if the person is suspected of carrying one or more man-made objects.