Focal Length

The focal length is the distance of the focal point of the lens to the imaging sensor. For the same imaging sensor, a larger focal length means a smaller field of view and more detail than a lower focal length which has a wide field of view with less detail. For structure from motion mapping, focal length is typically in a range of 5-30mm. In summary, the focal length affects the field of view of the sensor and the image’s spatial resolution. This will affect the required flight altitude and side-lap to achieve respective spatial resolution and side-lap percentage.