The volcanic Trindade Island is a remote Brazilian offshore territory in the South Atlantic, located ca. 1.140 kilometers east of the southeast coast of Brazil. The island's permanent exposure to geological hazards requires assessment. However, the lack of erosion and landslides temporal data impedes predictive geohazard analyses. Therefore, we compiled pre-existing data from nautical charts and surveyed the surface terrain on Trindade Island to generate Digital Terrain Models (DTMs) and comparative accuracy analyses. The DTM based on pre-existing data shows the lowest accuracy (root mean square error -RMSE: 12.3 m) yet is adequate for regional studies. In contrast, the DTM developed from real-time kinematic global navigation satellite systems (RTK-GNSS) has the highest vertical accuracy (RMSE: 0.48 m), but spatial variability of ground elements was underestimated and limited to meter-sized (and larger) elements. The DTM obtained using the unmanned aerial vehicle (UAV) with ground control points (GCP), on the other hand, presented lower accuracy (RMSE: 2.37 m) than the RTK-GNSS model but still allowed observation of centimetric (and larger) ground features. For geohazard assessment on Trindade Island, models that allow fine-scale studies are needed. A UAV with GCP provides such standards and proved to be the most viable option in remote and complex sites as well. Hence, this study, the first to allow multi-temporal analysis of geohazard assessment on Trindade Island, offers a viable solution for similar analyses in other remote locations.
Neste estudo demonstramos a eficácia da aplicação de tecnologias na aquisição de dados da superfície do terreno, para análises e monitoramento em detalhe, nas vertentes degradas pela erosão hídrica. Neste ensaio, aplicamos os métodos de aquisição por Veículo Aéreo não Tripulado (VANT) associados com Sistema em Tempo Real de Posicionamento por Satélite (RTK GNSS) na Ilha da Trindade. Tais métodos perimitem gerar produtos topográficos que viabilizam análises espaciais e temporais dos processos erosivos perigosos na região ocupada da ilha. Os resultados demonstraram que a área de estudo apresenta uma intensa erosão linear condicionada pela ação do escoamento superficial, ocorrendo desde erosões no estágio inicial, nas porções mais altas das encostas, até erosões lineares profundas nas porções a jusante próximas da ocupação. As técnicas aplicadas também explicitam as áreas críticas que devem ser preservadas e remediadas.
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