What is the difference between active sensor and passive sensor ?
An active sensor emits energy or signals to interact with the environment and detect objects or phenomena. It actively transmits pulses of energy, such as radar or lidar sensors, and analyzes the reflected or emitted signals to gather information.
A passive sensor detects and measures natural energy emitted or reflected by the object or phenomenon being observed. It does not emit any energy or signals of its own but relies on ambient energy sources, such as sunlight or thermal radiation. Examples include optical cameras and infrared sensors.
Active detection involves actively probing the environment using emitted energy or signals (like radar or sonar) to detect and locate objects. It relies on the reflection or echo of the emitted energy to identify objects.
Passive detection observes the environment without emitting any energy. It detects the naturally emitted or reflected energy (like electromagnetic radiation or acoustic signals) from objects or phenomena. Passive detection methods include thermal imaging and radio telescopes.
Active speed sensors directly measure the speed or velocity of an object by actively emitting signals (like radar guns) and analyzing the reflected signals to determine speed.
Passive speed sensors determine speed indirectly by observing changes in natural phenomena caused by an object’s movement. For example, passive infrared sensors can detect the heat emitted by a moving object and estimate its speed based on the observed change over time.
An active sensor is a device that actively emits energy or signals into the environment to gather information about objects or phenomena. It requires a power source to operate and typically involves transmitting and receiving components to analyze reflected or emitted signals.
A passive sensor detects and measures natural energy emitted or reflected by objects or phenomena without emitting any energy of its own. An example is a satellite sensor that observes Earth’s surface by measuring the sunlight reflected from it or the thermal radiation emitted by the surface.
In GIS (Geographic Information System), active sensors collect data by emitting energy and measuring its return (like radar or lidar), while passive sensors record naturally occurring energy (like sunlight or thermal radiation). Active sensors provide precise distance and elevation measurements, while passive sensors offer spectral information about the Earth’s surface.