*3.3. Flight Planning and Control*

To collect high-quality data, it is necessary to carefully plan the UAV flight according to the technical limitations and attributes of the platform, its equipment, and sensors. To create the plan, it is first necessary to conduct visits to the site or gain access to detailed maps. A plan can then be created in stages:


The photogrammetric block is determined by the size and location of the archaeological site and comprises take-off and landing points, along with the initial flight direction. From a theoretical perspective, the plan includes external orientation parameters (spatial and angular positions: X0, Y0, Z0, ω, ϕ, and κ) and internal camera parameters (principal point and principal distance: X0, Y0, and *c*). The latter are set by the manufacturer of the camera. Once these parameters have been determined, it is possible to calculate the scale, flight altitude, side and forward image overlaps, number of strips, and number of images to be collected for each strip. If the platform does not feature gyro-stabilization, incorrect positioning will likely occur, necessitating the use of GNSS observations, i.e., GCPs (Figure 4). The final step is to ensure that the flight adheres to the original flight plan. This is accomplished using geometric controls, which ensure that the thresholds do not exceed certain criteria:


**Figure 4.** Ground control points (GCPs) designed in a white and pink pattern.

As this particular platform type has no gyro-stabilizers and the GNSS is not highly accurate, it is necessary to use relatively wide limits to control the capture of images geometrically. Forward and side overlap limits are set at a minimum of 80% and 40%, respectively, while the error of the camera position is 3 m, and errors for the angular deviations are 0.2◦ (ϕ), 2◦ (ϕ), and 0.2◦ (κ). The greatest variation is 10% over the mean GSD size. Flight directional changes are restricted to a maximum of 2◦.

The flight was planned at an approximate altitude of 50 m, over an area of approximately 1 ha. The flight captured a total of 417 images in three west–east strips, with ten images per strip, a minimum forward overlap of 80%, and a minimum side overlap of 40% (Table 1).


**Table 1.** Specifications of unmanned aerial vehicle (UAV) flight planning.

**Figure 5.** Overlap and sidelap images established from flight planning and control.
