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|Validação De Mosaicos Aerofotogramétricos Utilizando Fotografias Obtidas Com Câmera Digital Não Métrica Acoplada A Um Vant.|
Autoria: Leomar Rufino Alves Júnior
Coautoria: João Batista Ramos Côrtes, Manuel Eduardo Ferreira
Abstract: The lack of updated maps on large scales of representation has driven the use of Unmanned Aerial Vehicles (UAV) for the generation of maps from different providers. This usage is mainly due to the low cost of equipment and the automation of the entire process, from taking the photos to the generation of orthomosaic. These facilities have allowed professionals with little or no cartographic experience using the UAV to generate maps. However, some questions arise: the orthomosaics generated by such systems come with cartographic precision desirable for their use? What problems can be identified at the junction of orthophotos to generate the orthomosaic? In order to answer these questions one aerophotogrammetric lifting a unit of environmental conservation was held in the city of Goiânia (Macambira Environmental Park). The flight plan was drawn up in the program e-mo-tion, provided by Sensefly - Swiss company UAV Swinglet CAM manufacturer used in this work. The camera installed on the UAV was the Canon IXUS 220 HS, with a spatial resolution of 12.1 megapixel CMOS sensor equipped with type 1/2,3” (4000 x 3000 pixel), pixel pitch of 1.54 μm, and distance 35 mm equivalent focal. The flight was performed at 331 m above ground, with a lateral overlap of 30% and 70% longitudinal, with planned spatial resolution of 10 cm, each shrouded photography 400 x 300 m, ie 12 ha. The photogrammetric block had 9 lines of flight, a total of 132 photographs, imaged with total area of 433.9280 ha. The orthophotos four orthomosaics were generated in Pix4Dmapper program. When performing aerial triangulation, the program determined both the calibration parameters of the camera. The first orthomosaic was generated without the use of control points, ie, we used the parameters of exterior orientation obtained directly by the inertial system and GPS on board the UAV. The other three were generated mosaics with 4, 8 and 16 pre-marked points of support. To check the precision and accuracy of orthomosaic were uniformly distributed in the block 46 pre-marked targets. The threedimensional coordinates of the target pre-marked on orthomosaic were read and compared with the coordinates obtained by geodetic survey of the RTK positioning method using a GNSS receiver signals. Evaluation of Cartographic Accuracy Standards (PEC) was performed by discrepancies between these coordinates. The bias was analyzed by student's t test and the accuracy of the chi-square probability considering the orthomosaic in scale 1/200 and Class A PEC as set out in Decree No. 89817 of 20.06.1984. It was found that in ortomosaics generated some buildings were not properly processed the conical projection to orthographic. The orthomosaics generated more than 4 control points were classified as Class A for the scale of 1/200.