# Review of Photogrammetric and Lidar Applications of UAV
## 6 Discussion
### Discussion on Applications of UAVs
#### 6.2.1 Mapping and Surveying
In the article [88], the authors investigated and validated the applicability of UAVs for updating cadastral records in areas affected by landslides. The mapped area was in Limanowa in Poland, covering an area of 70 hectares, with the flight height varying over each line individually. The UAV used DJI S1000 with a Sony ILCE A7R sensor, a Sony FE 35 mm F2.8 lens, and a Zenmuse Z15-A7 gimbal. In total, 465 images were taken, of which 388 were used for processing. The purpose was to obtain the analysis results in four variations with a different number of control points and methods of measurement. Orthophoto maps and DSM were used to update the cadastral data. The maximum deviation for each control point did not exceed 10 cm. This research concluded that a larger number of control points should be used to create photogrammetric products, ensuring accurate and correct models. The article [89] demonstrates the use of UAV technology in cadastral mapping, where automatically extracted boundaries are obtained from images. The boundaries were extracted using the ENVI feature Extraction (FX) module. The research was carried out in Slovenia in the municipality of Ponova. The area of the subject territory was 25 ha. A total of 12 GCP were used, evenly distributed over the mapped area, and determined by GNSS/RTK. For photogrammetric imaging, DJI Phantom 4 Pro with a 1'' CMOS 20 Mpix sensor was used. The UAV flew at a height of 80 m AGL, with a GSD value of 2 cm. The results of the accuracy evaluation showed that almost 80% of the extracted visible boundaries were correct. In the paper [90], the authors discussed UAV technology to assist in verification surveys of land boundaries in digitized cadastral territories. This case study was conducted in Taiwan in the ChengDa district of Taipei City. The flight was conducted at a height of 300 m AGL using an AI-RIDER YJ-1000-HC UAV with a PhaseOne iXU150 medium-format camera. As a result, 230 images were acquired, and the GSD accuracy was 3 cm. The research shows the possibility of generating one cadastral map consistent with the actual details of the terrain. This approach can reduce human resource costs and improve the efficiency of future boundary verification surveys. The article [91] discusses the mapping of large cadastral areas using UAVs. A rice field area of 80 ha in Trimuloy municipality, Indonesia, was selected for the research. In total, nine GCPs with a 12 cm RMSE were used. The flight was performed at a height of 250 m AGL, with a GSD value of 7.77 cm. The flying equipment was an RC high wing with a Nikon COOLPIX AW-120 photogrammetric sensor. This article demonstrates the successful use of a UAV-based remote sensing system to produce orthomasacics as base maps for cadastre. The research in the paper [92] discusses a technique based on deep fully convolutednetworks (FCN) that can automatically learn high-level spatial features from images to extract cadastral boundaries. For this research, the Busogo study area located in Rwanda was selected. In 2018, [PERSON] used a UAV to image the area and obtained photographs that were subsequently analyzed. The article [93] focuses on implementing UAV-based GNSS CORS UDIP to improve cadastral survey and urban development monitoring. The area of interest for this research was the city of Nyresep, which was flown over using a DJI Phantom 3 Professional with a Sony EXMOR sensor. The flight was conducted at a height of 182 m AGL. A total of 1387 images were acquired and subsequently processed. Fifteen GCPs were placed in the field, and coordinates were determined using the static GNSS method. The result is an ortho-mosaic with a GSD value of 7.86 cm, which can be used to delineate parcel boundaries and create a base map. Lidar and photogrammetry based on UAV can be effective methods in their applications in the field of real estate cadastre. These methods achieve reliable accuracy but lack completeness of the performed survey. Furthermore, the use of UAVs appears to be a suitable method when a large proportion of boundaries are visible.