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: Step 1. Before Starting a Project > 1. Designing the Image Acquisition Plan.

For more information about configuring the camera settings: Step 1. Before Starting a Project > 2. Configuring the Camera Settings.