What is the difference between active and passive remote sensing systems in geography?

Answer 1

Active remote sensing transmits energy to allow an image to be formed.

Passive remote sensing collects energy reflected or emitted from a surface.

Active systems direct a bean of energy at a surface and analyze the energy reflected back. An example of active sensing would be a radar.

Passive systems are pretty much what the eyes see, and it's like a photograph. Passive sensing radiates visible light.

Answer 2

Active remote sensing systems emit their own energy source (such as radar or lidar) to interact with the target and measure the reflected energy, while passive remote sensing systems rely on detecting natural sources of energy (such as sunlight or thermal radiation) reflected or emitted by the target. Active systems provide more control over the data collection process but require more energy and equipment, while passive systems are less expensive and less complex but are limited by the availability of natural energy sources.