# Optimal Ground Sampling Distance (GSD)

Hi There,

Whats the acceptable Ground Sampling Distance (GSD) for a accurate survey? Say a golf course?

I was thinking 2cm GSD maybe lower, any help on this is appreciated.

Thanks

Allan

Hi Allan,

If you know the level of accuracy you would like to achieve, you can calculate your optimal flight altitude by calculating your estimated ground sampling distance (GSD). GSD refers to the linear distance that one pixel accounts for. For instance, if you have a GSD of 3 cm/pixel, you know that each pixel accounts for 9 square cm on the ground.
TOOLS - GSD calculator

The accuracy of a correctly reconstructed project is expected to be 1-3 times the GSD. This error is not global. The accuracy of a point depends on the many parameters, such as the number of images that it is visible, the GSD in the area, how close it is in a GCP, etc.
However, for sub-centimeter GSD projects it is harder to get the ideal conditions. Problems such as the perspective, vibrations of the camera, blur effect, depth of field, etc. are magnified. It is recommended to do very careful testing and planning for such projects, in order to get the expected accuracy. Rolling shutter cameras are not recommended for sub-centimeter accuracy results.
Having this in mind, I would say that 1.5 cm is a quite good GSD that can generate quite accurate results. The level of details of the point cloud depends also on the type of the terrain you are trying to reconstruct, as well as the quality of the initial images and their visual content.

Please keep in mind that even when flying at a constant height, the images of a project will probably not have the same GSD due to terrain elevation differences and changes in the camera angle.

Ground sampling distance (GSD)
[How to select Camera Focal Length and Flight Altitude considering the desired Ground Sampling Distance and Terrain to map?

](https://support.pix4d.com/hc/en-us/articles/202558849)Hope this will help,
Best,