Atmospheric Correction

Atmospheric correction is a critical preprocessing step in remote sensingRemote SensingRemote sensing is the science of collecting data about Earth's surface without direct physical contact, primarily usi... that removes distortions introduced by the Earth's atmosphere from satellite and aerial imageryAerial ImageryAerial imagery involves photographs taken from planes or drones, offering detailed views of Earth's surface. It is a .... When electromagnetic radiation travels between Earth's surface and a sensor in orbit, atmospheric gases, aerosols, and water vapor scatter and absorb portions of the signal, altering the recorded values. Without correction, these atmospheric effects can lead to inaccurate analyses, unreliable spectral indices, and inconsistent multi-temporal comparisons. How atmospheric correction worksTwo primary approaches are used. Relative correction methods normalize images to a common radiometric baseline using pseudo-invariant features such as dark objects or bright targets without modeling the atmosphere explicitly. Absolute correction methods, such as FLAASH, 6S, and Sen2Cor, use radiative transfer models that account for sun angle, sensor geometry, atmospheric composition, and terrain to convert top-of-atmosphere radiance to surface reflectance. Why it mattersAccurate surface reflectance is essential for computing vegetation indices like NDVINDVIThe Normalized Difference Vegetation Index (NDVI) is a widely used spectral index that quantifies vegetation health a..., performing multi-date change detectionChange DetectionChange detection uses geospatial data and imagery to track and analyze alterations in landscapes, infrastructure, or ..., and comparing imagery acquired under different atmospheric conditions. Analysis-ready data (ARD) products from Landsat and Sentinel-2 are now distributed with atmospheric correction already applied, dramatically reducing the processing burden for end users. Atmospheric correction underpins the quantitative use of optical remote sensing data. As cloud-based platforms deliver pre-corrected imagery at scale, more analysts can focus on extracting insights rather than preprocessing, accelerating the pace of environmental monitoringEnvironmental MonitoringEnvironmental Monitoring is the systematic collection and analysis of data about environmental conditions, including ... and geospatial analysisGeospatial AnalysisGeospatial analysis applies statistical methods and specialized software to interpret spatial data, uncovering patter....