SLAR = USGS Side Looking Airborne Radar Mosaics: 1981 - 1990

The Side-Looking Airborne Radar (SLAR) is an image-producing system that derives its name from the fact that the radar beam is transmitted from the side of the aircraft during data acquisition SLAR is an active sensor; the system provides its own source of illumination in the form of microwave energy. Consequently, imagery can be obtained either day or night. Since microwave energy penetrates most clouds, SLAR can be used to prepare image maps of cloud-covered areas. Data are X-band synthetic aperture radar (horizontally transmitted, horizontally received) with the exception of some test sites. Since the radar signal is transmitted at a depressional angle below the horizontal plane in which the aircraft is flying, the signal strikes the terrain at an oblique angle, and the surficial expression of the geologic structure may thus be enhanced. The topographic expression of some surface features, such as subtle faults and folds, may be more clearly seen on radar imagery than on conventional aerial photographs or satellite images.侧视机载雷达（Side-Looking Airborne Radar，SLAR）是一类成像系统，其命名源于数据采集阶段雷达波束从航空器侧方发射的工作机制。SLAR属于主动传感器，该系统以微波能量作为自主照明源。正因如此，无论白昼黑夜均可获取成像数据。由于微波能量能够穿透绝大多数云层，SLAR可用于生成云层覆盖区域的影像地图。除部分测试站点外，本次所用数据均为X波段合成孔径雷达（X-band synthetic aperture radar，采用水平发射、水平接收的极化方式）。由于雷达信号以低于航空器飞行水平面的俯角发射，信号将以斜射角度入射地表，进而可强化地质构造的地表显现特征。部分地表特征（如细微断层与褶皱）的地形表现，在雷达影像上相较常规航空摄影照片或卫星影像更为清晰可辨。