Ground Sample Distance

Ground sample distance tells you how much ground distance is represented by one image pixel, so it is a direct measure of image scale. The formula comes from similar triangles in a pinhole-camera model: as flight height increases, each pixel covers a larger patch of ground, while a longer focal length projects a narrower field of view and makes each pixel cover less ground. Smaller sensor pixels also sample the image more finely, which lowers the ground area per pixel.

Use this when planning drone or aerial surveys, estimating map resolution, or checking whether imagery is detailed enough for tasks like surveying, crop monitoring, or object detection. It is also useful for comparing image quality across different cameras, altitudes, or lens settings.

• Using altitude above sea level instead of height above the ground being imaged
• Mixing units, such as putting H in meters while p and f are in centimeters
• Assuming GSD is constant everywhere in a tilted image or over uneven terrain