Aerial reconnaissance

Aerial reconnaissance is the collection of information about places or forces from aircraft, balloons, or other airborne platforms, using observation or sensors.

Aerial photography: The practice of photographing the ground from an aircraft or other elevated platform. Photographs preserve visible details that aerial reconnaissance can interpret and compare.
Observation balloon: A tethered or free-floating balloon used to observe terrain or enemy activity from above. Balloons were among the earliest platforms used systematically for military aerial observation.
Battlefield surveillance: The ongoing observation of an area of operations to detect changes, threats, and activity. Aerial reconnaissance can reveal troop positions and movement across a battlefield.
Satellite reconnaissance: The collection of information about Earth from satellites, using imaging or other sensors. Satellites observe from orbit, avoiding airspace incursions but offering different revisit times and resolution.
Synthetic-aperture radar: A radar technique that synthesizes a large antenna aperture from the motion of a transmitting platform. It can image terrain through clouds and darkness, extending reconnaissance beyond visible-light conditions.
American Civil War: The United States war from 1861 to 1865 between the Union and the Confederacy. Both sides used observation balloons to watch troop movements and battlefield positions.
Cartography: The making and study of maps. Aerial images supply measurements and geographic details for creating and updating maps.
Human intelligence: Intelligence gathered from information provided by human sources. Human sources can explain intent and context that airborne sensors cannot directly observe.
Photogrammetry: The measurement of objects and terrain from photographs, especially overlapping images. Overlapping reconnaissance photographs can yield maps, elevations, and measured distances.
Aerial photography in World War I: The systematic use of aircraft-mounted cameras to record military positions during the First World War. World War I made photographic reconnaissance a central, organized military practice.

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