Active Remote Sensing
Definition
Active remote sensing systems emit energy (e.g., radar, lidar) and measure the reflected signal to map surfaces. Unlike passive sensors, they operate independently of sunlight and can penetrate clouds/vegetation. Examples include SAR (Synthetic Aperture Radar) and airborne lidar.
Application
Lidar is used for high-resolution elevation modeling in forestry and flood risk mapping. SAR monitors ground deformation (e.g., volcanoes, landslides) and ice sheet dynamics. Military applications include terrain mapping under cloud cover. Autonomous vehicles use lidar for obstacle detection. NASA’s GEDI mission employs lidar to study forest biomass.
FAQ
1. How does active sensing differ from passive?
Active systems emit their own energy; passive relies on external sources (e.g., sunlight).
2. What wavelengths do active sensors use?
Microwave (radar), infrared (lidar), or radio.
3. Can active sensors work at night?
Yes, as they don’t require sunlight.
4. What’s a key disadvantage of active sensing?
Higher power consumption and cost compared to passive systems.
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