1. A wideband synthetic aperture radar (SAR) imaging system, comprising: a probe having an aperture through which a signal is transmitted incident to an object located in a medium of interest remotely from the probe and through which a plurality of nonuniformly sampled reflected signals from the object are received by the probe as the probe moves in a measurement plane located a predetermined distance from the object; a memory for storing measurement data representative of the reflected signals collected by the probe; a processor executing a plurality of computer-executable instructions for a SAR-based reconstruction algorithm, said instructions comprising: instructions for performing a spectral estimation based on the measurement data; instructions for transforming a frequency component of the spectral estimation as a function of the medium of interest; instructions for obtaining a three-dimensional SAR image from the transformed spectral estimation data using Fourier transforms; and a display responsive to the processor for presenting the three-dimensional SAR image to a user.