Active Remote Sensing


Active Remote Sensing is a type of remote sensing that involves the emission and subsequent reception of radiation from a source. The sensor emits its own energy and measures the strength and time delay of the returned signal, allowing it to gather information about an object or area of interest.

The radiation emitted by the sensor interacts with the target, and the reflected, refracted or scattered radiation is recorded by the sensor. This recorded signal is then processed and analyzed to extract useful information about the object or environmental factors.

What is Active Remote Sensing?

Active Remote Sensing is a technique that is commonly used in the field of geographical information systems (GIS) and environmental science. Unlike passive remote sensing, which relies on the natural radiation that is reflected or emitted from the observed scene or object, active remote sensing operates by emitting an energy pulse and detecting the intercepted or back-scattered signal.

Active remote sensing systems include Lidar (Light Detection and Ranging), SAR (Synthetic Aperture Radar), and sonar. These systems are typically used to measure the distance, speed, direction, or other properties of a scene or object, including its relative roughness or three-dimensional characteristics.

These systems are particularly useful for applications like surveying the topography of the Earth, where the direct measurement of distances from the sensor to the terrain surface is required. They also perform effectively at night and through dust, cloud, or fog, which can severely limit the performance of passive sensors.


What is the primary difference between Active and Passive Remote Sensing?

The main difference lies in the source of radiation. Active remote sensing systems use their own source of radiation, whereas, passive systems rely on natural radiation, typically from the sun or thermal infrared radiation emitted from the Earth.

What are some specific applications of Active Remote Sensing?

Active remote sensing has a wide range of applications, from climate change studies and disaster management to civil engineering and urban planning. Specific tasks may include terrain mapping, vegetation structure detection, ocean depth detection, and health monitoring of infrastructure.

What is a common example of an Active Remote Sensing system?

Lidar is a common and well-known example of an active remote sensing system. It uses a laser to emit a pulse of light and then measures the amount of time it takes for the light to return to the sensor to calculate the distance between the sensor and the object.

Why is Active Remote Sensing important?

Active remote sensing provides reliable and accurate data, regardless of the lighting conditions or the presence of obstacles such as clouds or dust. This ability to operate effectively in a wide range of conditions makes it an invaluable tool for geographical and environmental studies.

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