orthomosaics

An orthomosaic (also orthomosaic or orthophoto mosaic) is a georeferenced, orthorectified image created by mosaicking multiple aerial photographs to form a single, uniform image. Orthomosaics are corrected for camera geometry and terrain relief so that the scale is constant across the image and ground distances can be measured directly.

The images are typically captured with drones or aircraft that provide substantial overlap (often 60–80%). Photogrammetric software identifies common features, estimates camera positions, and performs bundle adjustment. A digital elevation or terrain model is used to remove distortions caused by relief. The corrected images are projected to a common map projection and blended into a seamless raster with a defined ground sampling distance (GSD).

Compared with simple image mosaics, orthomosaics maintain a stable scale across uneven terrain and provide a map-ready layer for GIS work and analysis.

Applications include land surveying, urban planning, agriculture, infrastructure monitoring, environmental assessment, and disaster response. Orthomosaics serve as basemaps, facilitate change detection, and support digitization and mapping workflows.

Limitations include dependence on input data quality, need for ground control points to improve absolute accuracy, shadows and occlusions, and edge artifacts where data are sparse. Accurate orthorectification also relies on a good digital elevation model and proper sensor modeling.