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Authors
Advisor(s)
Abstract(s)
A barragem do Alto Rabagão, concluída em 1964, deixou total ou parcialmente submersas várias aldeias
e elementos arqueológicos de grande valor histórico. Com o auxílio de fotografias aéreas históricas de um voo realizado em 1949 pelo SCE, pretende-se recuperar a paisagem primitiva correspondente à área inundada, com o intuito de identificar tais elementos.
A fase inicial consistiu na seleção e digitalização das fotografias que cobrissem a zona de estudo. No ArcMap foi feito o enquadramento dessas fotografias sobre as respetivas folhas em formato digital. Com base neste enquadramento e com auxílio de um mapa base, seguiu-se a escolha dos PFs, cumprindo diversos requisitos. Os pontos foram coordenados em ETRS89, nos modos RTK ou rápido-estático e utilizando a rede SERVIR (IGeoE). Dois PFs não foram coordenados devido a restrições de acesso no terreno. Após o ajustamento das coordenadas obtidas pelo método rápido-estático, as coordenadas finais permitiram então elaborar as fichas definitivas de todos os PFs.
A orientação espacial do bloco da cobertura fotográfica foi determinada no ISAT através de uma triangulação aérea automática, com um sigma (desvio padrão) final de 4.8 μm (abaixo da tolerância definida de 20 μm). No ISAE foi extraída automaticamente uma malha de pontos, base para o MDS. Para evitar a possível existência de vários valores de cota para os mesmos pontos, as zonas de sobreposição entre modelos sucessivos de cada fiada foram eliminadas no MicroStation. No ArcMap, a nova amostra de pontos foi convertida numa TIN, gerando o MDS. No ArcScene, um raster, gerado a partir da TIN, foi adicionado como superfície base para definição da altitude ao mosaico das ortofotos da zona de estudo, criado previamente no ISOP. O produto final foi um modelo tridimensional com a textura real do terreno, que está atualmente a ser estudado e analisado por arqueólogos.
The Alto Rabagão dam, completed in 1964, left wholly or partially submerged several villages and archaeological sites of great historical value. With the aid of historical aerial photographs of a flight conducted in 1949 by SCE, it is intended to recover the original landscape corresponding to the flooded area, in order to identify such features. The initial phase involved the selection and digitalization of the photographs that covered the study area. Using ArcMap, the photographs were framed over the respective digitalized sheets. Based on this framework and with the aid of a base map, a set of PPs was chosen, fulfilling several requirements. The points were coordinated in ETRS89, with RTK or rapid-static modes and using the SERVIR network (IGeoE). Two PPs were not coordinated due to terrain access restrictions. After the adjustment made to the coordinates obtained by the rapid-static mode, the final coordinates allowed the elaboration of all PPs’ definite forms. The blocks’ photographic coverage spatial orientation was determined in ISAT through an automatic aerial triangulation, with a final sigma (standard deviation) of 4.8 μm (under the defined tolerance of 20 μm). A point mesh, serving as a basis for the DSM was automatically extracted in ISAE. To avoid the possible existence of multiple elevation values for the same points, the overlapped areas between successive models of each row were eliminated in Microstation. Using ArcMap, the new point mesh was converted into a TIN, generating the DSM. In ArcScene application, a raster surface, generated from the TIN, was added as a basis for setting the altitude to the study area orthophotos mosaic, previously created in ISOP. The final product was a tridimensional model with the actual terrain texture, which is now being studied and analyzed by archaeologists.
The Alto Rabagão dam, completed in 1964, left wholly or partially submerged several villages and archaeological sites of great historical value. With the aid of historical aerial photographs of a flight conducted in 1949 by SCE, it is intended to recover the original landscape corresponding to the flooded area, in order to identify such features. The initial phase involved the selection and digitalization of the photographs that covered the study area. Using ArcMap, the photographs were framed over the respective digitalized sheets. Based on this framework and with the aid of a base map, a set of PPs was chosen, fulfilling several requirements. The points were coordinated in ETRS89, with RTK or rapid-static modes and using the SERVIR network (IGeoE). Two PPs were not coordinated due to terrain access restrictions. After the adjustment made to the coordinates obtained by the rapid-static mode, the final coordinates allowed the elaboration of all PPs’ definite forms. The blocks’ photographic coverage spatial orientation was determined in ISAT through an automatic aerial triangulation, with a final sigma (standard deviation) of 4.8 μm (under the defined tolerance of 20 μm). A point mesh, serving as a basis for the DSM was automatically extracted in ISAE. To avoid the possible existence of multiple elevation values for the same points, the overlapped areas between successive models of each row were eliminated in Microstation. Using ArcMap, the new point mesh was converted into a TIN, generating the DSM. In ArcScene application, a raster surface, generated from the TIN, was added as a basis for setting the altitude to the study area orthophotos mosaic, previously created in ISOP. The final product was a tridimensional model with the actual terrain texture, which is now being studied and analyzed by archaeologists.
Description
Tese de mestrado em Engenharia Geográfica, apresentada à Universidade de Lisboa, através da Faculdade de Ciências, 2012
Keywords
Fotogrametria Fotografias aéreas antigas Orientações Triangulação por feixes perspetivos Ortofotos Modelo digital de elevação Teses de mestrado - 2012