High-resolution Synthetic Aperture Radar (SAR) images produced by ERS-1/2 of the same region, and taken several days or weeks apart, can be combined by computer to create multitemporal images. The individual exposures are treated as quasi-colour extracts and combined to produce a single image. Parts of the picture in which identical radar echoes are recorded during all of the overpasses then appear in the multitemporal image in varying tones of grey, while parts appearing in colour are evidence of changes having occurred.The multitemporal image seen here shows an area about 80 km square on the west coast of central Italy, including the Gulf of Gaeta some 120 km SE of Rome; it was compiled using the first SAR image from ERS-2 on 2 May 1995 (red channel) and two ERS-1 images (taken on 27 March [blue] and 1 May 1995 [green]).The mountains at left are up to 1000 m high and separate the valley of the River Liri (to the north) from the Tyrrhenian Sea. Running through this valley, and seen as a thin black line, is the famous Autostrada del Sole motorway joining Rome and Naples. The light patch above this, near the top edge, comes from the strong reflection of the radar waves in the region of an extensive industrial complex. The righthand part of the picture is dominated by a volcanic structure, the Roccamonfina, whose slopes exhibit clear traces of erosion as a pattern of radiating stripes. The evident colour differences over the sea reveal differing wind conditions during the various overpasses, while the yellow in flat land areas is due primarily to differences in soil moisture content or in the coarseness of the ground surface.Data received at Fucino (I), image processing by ESA/ESRIN, Frascati (I). [Image Date: 18-05-95] [95.05.011-001]