This article points out three important factors to take into consideration when designing an image acquisition plan.

In order to have high-accuracy results in the most efficient way, a high overlap between the images is required. Therefore, the image acquisition plan has to be carefully designed in order to ensure enough overlap. The image acquisition plan depends on the required GSD by the project specifications and the terrain type/object to be reconstructed. A bad image acquisition plan will lead to inaccurate results or processing failure and will require acquiring images again.

When designing the image acquisition plan the following factors need to be taken into consideration:

• Image acquisition plan type: The image acquisition plan type depends on the type of terrain/object to be reconstructed.
• Ground Sampling Distance (GSD): The required GSD by the project specifications will define the distance (flight height) at which the images have to be taken. For more information: Ground sampling distance (GSD) in photogrammetry
• Overlap: The overlap depends on the type of terrain that is mapped and will determine the rate at which the images have to be taken.

Nowadays, technologically advanced UAVs come with very good software that can design the image acquisition plan given some parameters (area of interest, the percentage of overlap between the images, the desired GSD, etc). In this case, the images are taken automatically by the UAV according to the selected image acquisition plan without any user intervention.

The design of the image acquisition plan consists of 3 steps:

a. Selecting the Image Acquisition Plan Type
b. Computing the Flight Height for a given GSD
c. Computing the Image Rate for a given Frontal Overlap