How to select Camera Focal Length and Flight Altitude considering the desired Ground Sampling Distance and Terrain to map?

It is important to consider the following facts:

  • At a defined altitude, increasing the focal length:
    • A smaller area is captured, and therefore:
    • The Ground Sampling Distance (GSD) value will decrease: one pixel will capture a smaller area and therefore the image will have a higher spatial resolution.
       
      Important: The image rate needs to be increased to maintain a good overlap.
  • At a defined focal length, decreasing the altitude:
    • A smaller area is captured, and therefore:
    • The GSD value will decrease: one pixel will capture a smaller area and therefore the image will have a higher spatial resolution.
       
      Important: The image rate needs to be increased to maintain a good overlap.

Terrains:

    • Forest and dense vegetation: Flying higher helps for the reconstruction, but the spatial resolution will be lower.
    • Buildings: Flying higher reduces the artifacts at the building edges, but the spatial resolution will be lower.

 

 

 

Overlap:

  • Low altitude with big focal length will request a very high image rate in order to maintain a good overlap.
  • For a given focal length and a given image rate, increasing the altitude will increase the overlap.

 

 

For more information about selecting the flight plan type, computing the flight height for a given GSD and computing the image rate to get a given overlap: 202557409.

For more information about configuring the camera settings: 202557419.

 

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