1. An imaging control arrangement for use with a transmission-reception means for transmitting pulses, which means has an array of receivers for receiving transmitted pulses after reflection and with imaging means for displaying in an image plane an image representing an object surface, the imaging control arrangement having: an input arrangement for receiving from the transmission-reception means echo signals conveying echo data relating to the distance away of reflective elements; an output arrangement for connection to the imaging means to feed control signals thereto; and, connected between the input and output arrangements, signal processing means for receiving the echo data and for defining therefrom, and from range information relating to the range of the object surface to be imaged, equitime loci in the object surface corresponding to the echo data, the equitime loci being the loci of all those object elements in the object plane which would give the same pulse transmission time from the transmitter to the object plane and back to the receiver, the signal processing means being operable to produce from these defined equitime loci said control signals for the imaging means such as to cause the display in the image plane of a plurality of image elements representing reflective elements substantially in the object surface by displaying image elements at positions corresponding to intersections of these equitime loci.