Remotesensing

Remote sensing is the science and technology of obtaining information about objects, areas, or events from a distance, typically using sensors on aircraft or satellites that detect reflected or emitted electromagnetic energy. It encompasses passive methods that measure natural energy and active methods that emit signals, such as radar or lidar.

Sensors capture data across a range of spatial, spectral, and temporal resolutions. Optical sensors collect visible, near infrared, and shortwave infrared data; thermal sensors measure emitted heat; radar and lidar provide active measurements that can penetrate clouds or vegetation. Platforms include satellites, airplanes, and unmanned aerial vehicles.

Processing involves radiometric and geometric correction, atmospheric correction, and projection to common geographic coordinates. Analysis uses image classification (supervised and unsupervised), change detection, spectral unmixing, and data fusion with other sources such as geographic information systems.

Major applications include land cover and land use mapping, agriculture and crop monitoring, forestry, water resources management, urban planning, environmental monitoring, disaster response, and climate research.

History and outlook: early aerial photography evolved into spaceborne sensing with satellites in the mid-20th century. The field has grown with modular sensors, higher resolutions, and new platforms such as small satellites and drones. Challenges include cloud cover, limited resolution, calibration, data volume, and processing requirements. Future trends emphasize higher resolution, hyperspectral sensing, synthetic aperture radar, data fusion, and automation through machine learning.