Question

Distinguish between the following:

Active and passive remote sensing systems.

Answer 1

Sr. No.	Aspect	Active Remote Sensing Systems	Passive Remote Sensing Systems
1.	Energy Source	Active remote sensing systems emit their own energy, usually in the form of electromagnetic waves.	Passive remote sensing systems rely on natural sources of energy, such as sunlight.
2.	Operation Time	These systems can operate both during the day and night.	These systems can operate only during the daytime if they depend on visible light.
3.	Weather Dependence	They are less affected by weather and atmospheric conditions.	They are affected by weather and atmospheric conditions.
4.	Examples	Examples of active remote sensing systems include radar and LiDAR.	Examples of passive remote sensing systems include cameras (using the visible spectrum) and thermal infrared sensors.
5.	Type of data	These systems measure the backscattered or reflected energy that they themselves emit.	These systems measure naturally emitted or reflected energy from objects.
6.	Advantage	The main advantage of active systems is that they are independent of external illumination.	The advantage of passive systems is that they can observe natural reflectance and thermal properties.