## 1 Introduction
When detailed models are required, low flight heights are recommended [29]; (2) speed: high speed may capture blurry images and affect the UAV's stability and manoeuvrability; (3) Ground Sample distance (GSD): this indicates the size represented by a pixel on the terrain [30] and is directly related to height, as the GSD is higher at greater heights, leading to lower spatial resolution; and (4) overlap: this is the partial superposition between two photographs in a frontal and lateral way. Increasing the percentage of overlapping provides better accuracy and optimises the object's shape. Photogrammetric software, such as PIX4D [31] and Agisoft Metashape [32], suggests that images be acquired with a forward overlap \(>\) 75% and lateral overlap equal to 60%. However, when an overlap of 90% is exceeded, the stereoscopic vision is lost in the photogrammetric reconstruction [28], increasing the processing time. * Georeferencing involves aligning spatial data or images with a specific geographic location using a coordinate reference system. This can be achieved through two main methods: direct and indirect georeferencing. Direct georeferencing is performed using a UAV equipped with an RTK (Real-Time Kinematic) system, which relies on a Global Navigation Satellite System (GNSS). In this method, the camera shutter is synchronised with the GNSS receiver, allowing each image to be geotagged at the moment of capture. Alternatively, the indirect method incorporates Ground Control Points (GCPs) for georeferencing and Checkpoints (CPs) for quality control [8]. Both GCPs and CPs can be measured using GNSS receivers or total stations. When high-precision instruments are used, this approach significantly reduces systematic errors in the final output. It is crucial to place GCPs and CPs at different locations, as the 3D model is optimised to the GCPs, resulting in minimal residual errors at those specific points [28]. To ensure optimal accuracy, a topographic survey should be conducted, with GCPs and CPs strategically distributed throughout the study area;
* There is the adoption of cameras equipped with mechanical rolling shutters or global shutters, which are ideal for photogrammetry, instead of electronic rolling shutters [33; 34]. In UAV applications, electronic shutters are widely used due to their higher burst shooting speeds, which enable rapid image capture in fast-moving scenarios, and their lack of mechanical wear ensures durability and reliability in high-vibration environments. These characteristics make electronic shutters particularly suitable for tasks such as video recording, documentation, and non-metric surveys. Despite their advantages, electronic shutters can suffer from rolling shutter distortion, causing skewing or artifacts during fast UAV movements or when capturing fast-moving objects [35]. Most cameras equipped on low-to-mid-range UAVs have a rotating shutter (this type of shutter currently occupies the UAV camera market). This makes them more affordable because they have a lower cost compared to UAVs with a mechanical shutter. The disadvantage of this type of shutter is that, when taking images, the image sensor is exposed line by line, which can introduce additional distortions in the image space, as the UAV navigates at a relatively high speed during aerial acquisitions. This implies that the electronic shutters have a small delay between the top and bottom of the image. Since version 2.1, Pix4 Dmapper Pro has implemented a rotating shutter correction model that corrects for this offset. It must be corrected when the vertical offset is greater than 2 pixels. Other photogrammetric software also has this type of correction, such as Agisoft metashape and MicMac [34]. The correction model takes into account the movement of the camera positions. These different camera positions for each row are approximated by applying a linear interpolation between the two camera positions at the beginning and at the end of the image reading.