Enter the flight altitude, sensor height, focal length, and image height into the calculator to determine the GSD.

GSD Formula

The following formula is used to calculate a ground sample distance.

GSD = ( A * SH) / ( FL * IH)

  • Where GSD is the ground sensor distance
  • A is the altitude
  • SH is the sensor width/height
  • FL is the focal length of the camera
  • IH is the image width/length

What is GSD (Ground Sample Distance) ?

GSD, short for ground sample distance, is a metric used with drone mapping and surveying to relate the focal length, resolution, and camera distance from the object.

Knowing all but one of any of the variables present in the formula above means a person can solve for the missing variable.

The units for GSD are distance per pixel, i.e. cm/pixel.

How to calculate GSD ground sample distance?

The following example problem outlines the steps needed to calculate a ground sample distance (GSD).

First, determine the altitude of the drone taking the image. In this example, the drone is flying at an altitude of 500 feet.

Next, determine the sensor width. Measuring the sensor width in this example yields .75 feet.

Next, determine the focal length of the camera. The focal length for this particular drone is found to be 6 feet.

Net, determine the image width/height. The image footprint on the ground is found to be 100 feet.

Finally, calculate the GSD using the formula above:

GSD = ( A * SH) / ( FL * IH)

GSD = ( 500 * .75) / (6 * 100)

GSD = .625