1. A method of imaging objects contained in a media, having a specific impedance which is different from the specific impedance of the medium, comprising applying current to the medium at various locations at a surface of the medium, extracting current at other locations, detecting voltages produced by the current which has passed through the medium from the surface of the medium at various other locations, successively determining a location of the object with increasing accuracy by processing values of the detected voltages determining a region in the medium in which the object is located from values of the detected voltages, successively determining a location and shape and conductivity of the object with increasing accuracy by processing values of the detected current, determining a pattern of convergence, selecting an appropriate function which approximates the determined pattern, extrapolating the function to a limit of an infinite number of iterations, and displaying an image illustrating the extrapolated functions on an axis at locations of the pattern of convergence.