The GSD is the real-world size of a pixel in your images, and for most drone flights it’s between 1 and 10 cm. A low GSD (1cm) is very high resolution imagery, and a high GSD means lower resolution.
The GSD is determined by:
- The resolution of your camera sensor — e.g. a 12MP camera will have a higher GSD than a 22MP camera
- The altitude of your flight — flying higher means a higher GSD
- The focal length/field of view of your camera — a wider angle camera like a GoPro means a higher GSD
In general, the final accuracy for a model in X and Y is 1–2x the GSD, and 1–3x in the vertical however you will find that the average error tends to be closer to 1x GSD for all axes.
Image source: Doug Corrin, Maps and Photogrammetry