# Review of Photogrammetric and Lidar Applications of UAV
## 5 Selected UAV Sensors and Their Applications
A DJI Phantom 4 Pro UAV equipped with a digital camera with a resolution of 5472 \(\times\) 3648 pixels was used to capture 1389 images from a height of 35 m. The parameter of ground sampling distance (GSD) was 0.01 m. The overlap of the images was set to 80%. For georeferencing, 16 GCPs were used. Their coordinates were determined using the spatial polar method, and their average total RMSE was 0.011 m. Data processing was carried out in the Agisoft Metashape Professional 1.5 software. The resulting point cloud contained 261 million points. The study [59] used a DJI Phantom 4 Pro equipped with a compact Parrot Sequoia multispectral sensor, which can capture RGB images with a resolution of 4608 \(\times\) 3456 pixels, to capture rice and wheat yields. The DJI Phantom 4 Pro together with the Parrot Sequoia  
Figure 2: Comparison of sensors GSD/RMSE vs. flight height. sensor weighed 1.746 kg. The authors performed flights at the altitudes of 30 m, 50 m, and 100 m. We focused on their flight at an altitude of 50 m AGL. Multispectral sensing of the area was performed in 10 min. Approximately 3 ha was covered, with the front overlap at 86% and the side overlap at 76%. On average, the root means square error (RMSE) at the control points was 37.2 cm. The ground sampling distance (GSD) was 4.3 cm in this case. The Parrot Sequoia multispectral sensor was also used by the UAV 3 DR Solo quadcopter, which is described in the literature [60]. The study was conducted in a private lychee orchard located 25 km southeast of Brisbane, consisting of 189 trees. The development and dynamics of tree growth and structure were monitored using UAV technology. At a height of 50 m AGL and a flight speed of 5 m/s, 278 images were acquired with 80% side and 85% forward overlap. The created DTM had a GSD of 6.5 cm, and the RMSE value was 0.25 m.  
The authors of [61] describe the application of surveying methods to study rock decay and geological hazards due to the erosive force of the Candigliano River in a natural slope in Italy. They used terrestrial laser scanning (TLS) and UAV-based digital photogrammetry. The flights were performed by the UAV DJI Phantom 4 PRO equipped with a 20-megapixel digital camera. Four flights were carried out at flight heights from 10 m to 80 m. A total of 1232 photographs were taken using 80 ground control points (GCPs). A front overlap of 80% and a lateral overlap of at least 60% were set. The average GSD of value 1.8 cm was achieved. Agisoft MetaShape 1.5.3 software was used to process UAV images, where a dense 3D point cloud was generated. The final point cloud contained 22,308,471 points, and the Root Mean Square Error (RMSE) was 80 mm. The literature [64] shows the use of a UAV on which a scanner was placed. The study area covered approximately 1963 ha and was located in the forests of eastern China. Lidar data were acquired using a Velodyne Puck VLP-16 laser scanner mounted on GV1300 multi-rotor UAV. The flight height was set to 80 m AGL, the flight speed to 4.8 m/s, and the overlap to 75%. Under such conditions, the average point density was 50.24 pts/m\({}^{2}\). Field data were processed in LiDAR360 software. The obtained result from the flight in this study showed that the data reached similar accuracy, but the use of lidar technology is financially expensive. Similarly, authors in the literature [62] monitored 178 trees in Furano City, Hokkaido Island, northern Japan. All 3292 images with a resolution of 5280 \(\times\) 3956 pixels were acquired using the Inspire-2 UAV with a mounted Zenmuse X55 RGB camera at a flight height of 120 m AGL and 80% overlap. The average achieved GSD was 2.3 cm. A total of 19 ground control points were placed in the area of interest. The resulting models were evaluated using the RMSE error. Its value did not exceed 2 cm in both cases. For photogrammetric processing of UAV data obtained by the Zenmuse X55 RGB sensor, the authors used the 3D modeling software Agisoft Metashape Professional Edition 1.5.3.