Summary form only given. The interferometric synthetic-aperture-radar (INSAR) imagery of the Monterey Bay is considered. Experimental data accumulated by INSAR over Monterey Bay cover both the shore areas and the ocean, and include two full complex SAR maps of the image area. The INSAR image of a given spatial location is obtained by the back antenna with the time shift Δt relative to the forward antenna. Identical portions of the INSAR and both SARs images were selected. The mean absolute value of the backscatter cross-section of the INSAR image, which has undergone partial fading due to the time delay, Δt, were obtained. The outcome was compared with the corresponding values for the both conventional SAR maps. By comparing these results, the decay of the covariance function during the time lap Δt (and thus the coherence time) was computed. The finite scene coherence time estimated directly in the present work is used to determine the effective azimuthal resolution of the obtained INSAR images.