Sitemark is pleased to announce the release of our Terrain Assist feature in the Sitemark Pilot App. Developed with pilots and customers in mind, Terrain Assist automatically calculates Ground Sampling Distance (GSD) and simplifies the process of flying in challenging terrain.

What is Ground Sampling Distance?

Ground Sampling Distance (GSD) is the spatial resolution of an image.  GSD in a digital photo (such as an orthophoto) of the ground from air or space is the distance between pixel centers measured on the ground. The bigger the value of the image GSD, the lower the spatial resolution of the image and the less visible are the details. GSD is also related to the flight height; the higher the altitude, the bigger the GSD value.

Why is GSD Important?

In simple terms, GSD is how big each pixel is on the ground.  If the elevation of the terrain changes and the distance between the drone and ground also changes, it will create an error in GSD and affect the accuracy and quality of data from your operation. A high-quality 3D model starts with high-quality data and a steady and consistent flight is critical to get the images right. Poorly captured drone imagery may mean having to go back on site to do it all over again — or worse, making operational or safety decisions based on bad data and paying the price later down the line.

Ground sampling distance image of drone moving over hilly terrain and showing no overlap
To the left of the picture, there is some overlap. As the drone moves to the right and elevation changes, there is no overlap and loss of data.

Ground sampling distance example showing if the drone changes its altitude with the terrain there is no loss of data
If the drone follows the terrain the GSD remains constant and there is no loss of data.

How Will Terrain Assist, Assist Me?

Terrain Assist automatically generates an optimized, intelligent 3D flight path to ensure constant GSD. For customers, this means high-quality, accurate data, and for the pilot, saved time, and reduced errors in the data acquisition process. By using automation, pilots no longer have to think about flight plans and flight altitudes anymore.

How Does it Work?

Sitemark's Full Stack Engineer, Rugen Heidbuchel, developed the feature to simplify the process of calculating GSD.

No formulas or calculations are needed; enable it within Sitemark's Pilot App, and you're ready to go.

With existing apps, the only solution is to divide the entire site into sections of relatively constant altitude. The pilot then has to move and stand next to the plane he/she was going to fly to get the relative altitude to be correct. This is only possible for sites that aren't too hilly because you would have to cut them into too many sections otherwise.

If existing customers would like to enable the feature, all they need to do is email

The more complex the terrain, the more complex the data capturing techniques tend to become. Terrain Assist is one of the many features from Sitemark that help customers and pilots acquire data in a better and easier way while ensuring compliance with high-quality data acquisition standards.

Contact us

If you're facing some challenging terrain in your next operation and you need our help, contact to find out more.