Off-Nadir Angle

The Off-Nadir Angle is one of the important factors in the satellite remote sensing process, which denotes the distance between the viewing direction of the sensors and the vertical, or nadir, direction. This factor has significant influence on the determination of the satellite image geometry, resolution, ground coverage, perspective, and positional accuracy. The larger off-nadir angle provides satellites an opportunity to record images outside the direct ground track. However, an increase in the viewing angle leads to more geometric distortions, longer shadows, and changes in the appearance of the terrain and objects. It is crucial to know about the off-nadir angle when choosing satellite images for the purpose of GIS mapping, Earth observation, urban planning, agriculture, disaster management, environmental monitoring, infrastructure evaluation, and change detection. This guide is intended to provide information about off-nadir viewing, its relation to nadir imagery, main advantages and disadvantages, and influence of viewing geometry on the geospatial data quality.