Earthobserving

Earth observation (EO) refers to the acquisition of information about the Earth's surface, atmosphere, and oceans through remote sensing and in situ measurements. EO combines data collected from spaceborne sensors, aircraft, drones, ships, and ground-based instruments to monitor environmental conditions, map land use, and study climatic and ecological processes. The information is used in scientific research, environmental management, disaster response, and policy development.

Remote sensing modalities include optical and infrared imagery, multispectral and hyperspectral data, radar (synthetic aperture radar, SAR), and LiDAR. Optical sensors capture reflected sunlight or emitted thermal radiation, while active sensors emit signals and measure returned energy. Data products encompass land cover and land use, vegetation health, surface temperature, moisture, topography, and atmospheric properties. Data are processed, standardized, and made available through GIS-compatible formats.

EO has roots in early satellite programs of the 1960s and 1970s, with Landsat beginning in 1972 and providing long-term land-imaging records. Other notable programs include ESA's ERS and Envisat missions, Japan's ALOS, India's Resourcesat, and the Copernicus program's Sentinel satellites. Many agencies now provide free or open access to a large portion of EO data, enabling broad use in science and applications.

Applications span agriculture, forestry, urban planning, water resources, meteorology, and disaster management. EO supports crop monitoring, drought assessment, flood mapping, wildfire risk, urban expansion analysis, and climate research. It is increasingly complemented by analytics, machine learning, and cloud-based processing to handle growing data volumes and enable near-real-time products.

Challenges include data volume and processing requirements, atmospheric and cloud interference for optical data, temporal and spatial resolution trade-offs, and privacy considerations. Ongoing trends emphasize constellations of small satellites for higher revisit frequency, advanced sensors, and open data policies that encourage interoperability and reproducibility in EO research and services.