In surveying, what does "ground control" refer to?

The term "ground control" in surveying specifically refers to fixed points that provide a reference for aerial surveys. These points, which are established with known coordinates, are crucial for maintaining accuracy in mapping and data collection from aerial imagery or remote sensing technologies. They serve as a stable framework against which measurements can be calibrated, ensuring that the data collected aligns with real-world positions and dimensions. Ground control points are essential for processes such as photogrammetry, where the accuracy of the aerial images depends on these referenced points to relate the two-dimensional imagery to three-dimensional features on the earth's surface. This allows for the production of reliable spatial data that can be used in various applications, including topographic mapping and geographic information systems (GIS).