The sensor width to achieve a GSD of 2.5 cm/px is 12.5 cm. Considering a drone flying at 100 m altitude having a camera with a focal length of 0.1 m and image width of 5000 pixels, the sensor width is given by:
S = 2.5 × 0.1 × 5000 / 100 = 12.5 cm. Read more