The Ground Sampling Distance (GSD) is the distance between two consecutive pixel centers measured on the ground. The bigger the value of the image GSD, the lower the spatial resolution of the image and the less visible details.
The GSD is calculated based on:
- The flight height / the distance from the terrain or object (H).
- The camera specifications:
- Image width (ImW).
- Sensor width (SW).
- Focal length (F)
Flight height (H) and camera specifications (ImW, SW, and F) influence the GSD.
It is important to decide on the GSD value before starting the image acquisition in order to adjust the flight height and the camera specifications to the project requirements. For example, when a detailed reconstruction of the area is needed, we recommend flying closer (low GSD) to the object of interest. On the other hand, when covering large areas that do not need very detailed results, flying higher (high GSD) can greatly reduce the acquisition time and batteries needed as well as reduce the processing time.