Resolution or Average GSD (Ground Sampling Distance) - the distance between two neighboring pixel’s centers measured on the ground.
The bigger value of the GSD, the lower the spatial resolution of the outputs.
GSD affects the accuracy of the outputs. The lower the GSD value, the more accurate can the project be georeferenced.
As a rule of thumb, the horizontal accuracy is around 2x GSD.
The vertical accuracy is around 3x GSD.
Here is an example of a parking lot section from one of our projects:
Native resolution: GSD = 1.5 cm/pixel
2D orthomosaic at a 1.5 cm/pixel resolution
Curbs, road paint and utilities are highly readable.
This is our standard resolution for Roof - Drone - Photogrammetry product.
GSD = 3.5cm/pixel
2D orthomosaic at a 3.5 cm/pixel resolution
Curbs, road paint and utilities are readable, but a bit less detailed than at smaller GSD value.
This is our standard resolution for Terrain - Drone - Photogrammetry product.
GSD = 10cm/pixel
2D orthomosaic at a 10 cm/pixel resolution
Curbs, road paint and utilities are much less readable and the accuracy in coordinate reference system is much worse.
This level of detail is usually achieved with manned aircraft photogrammetry.
With drones we stick to lower GSD and therefore better accuracy.
GSD = 20cm/pixel
2D orthomosaic at a 20 cm/pixel resolution
Curbs, road paint and utilities are unreadable and the accuracy in coordinate reference system is much worse.
This level of detail is usually achieved with manned aircraft photogrammetry.
With drones we stick to lower GSD and therefore better accuracy.
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The value of Average GSD is influenced by:
Flight altitude above ground level – the lower a drone will fly, the lower the GSD,
Focal length of the camera lens – the longer the focal length of the camera, the lower the GSD,
Sensor size - The bigger the sensor, the better,
Sensor resolution – The more megapixels a camera has, the better,
Terrain elevation difference – this affects the distance between camera and the ground, just as flight altitude,
Camera angle – if the camera is tilted, the GSD value increases,
Quality of images - blurry images will increase the value of the GSD.