A tomography system for analyzing an object concealed within an enveloping surface. The system has multiple beams of penetrating radiation, each beam disposed with a distinct orientation with respect to the enveloping surface. Detectors are provided for measuring radiation backscattered by the contents of the enveloping surface and for measuring radiation transmitted through the enveloping surface. The enveloping surface is moved with respect to the multiple beams, and a timer provides for measurement of a time difference between the appearance of features in signals of respective detectors, allowing geometrical characteristics of the features to be determined and displayed.