georeferentsed

Georeferentsed are ground control points—points on the Earth's surface with precisely known geographic coordinates—that are used to assign real-world location information to spatial data and to align different datasets within a common coordinate system. They provide external reference for the georeferencing or geocontextual placement of imagery, maps, or point clouds.

In practice, georeferentsed are collected in the field using accurate positioning methods such as GNSS (Global Navigation Satellite System), differential GNSS, or traditional surveying instruments. The coordinates of these points are then matched to corresponding features in the dataset to be georeferenced, allowing a mathematical transformation to be computed. This transformation (which may be affine, projective, or higher-order) links image or model coordinates to geographic coordinates, minimizing residual errors at the control points.

The quality of georeferencing depends on several factors: the number of georeferentsed, their spatial distribution across the data, the accuracy of the point coordinates, and the complexity of the transformation required. More well-distributed control points generally yield more robust results and lower positional error, especially toward the edges of an image or scene.

Georeferentsed are used in a range of workflows, including converting aerial or drone imagery into geospatially accurate maps, aligning historical maps with contemporary datasets, and coordinating multisource data such as LiDAR and satellite imagery. They are distinguished from tie points, which support internal alignment when absolute coordinates are not required.

Limitations include the need for field measurements, environmental access, and changes over time that may affect point locations. Proper metadata and accuracy reporting are essential for reproducibility and data quality.