Passive Remote Sensing:
•Natural sources of radiation, the attenuated, reflected, scattered, or emitted radiation is analysed:
•solar light
•lunar light
•stellar light
•thermal emission
•Active Remote Sensing:
•Artificial source of radiation, the reflected or scattered signal is analysed:
•sound: SONAR
•radio waves: RADAR (RAdioDetection And Ranging)
•laser light: LIDAR (LIghtDetection And Ranging)