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Caracterização 3D de movimentos de massa em terrenos com permafrost nas Ilhas Shetland do Sul (1956 - 2010) através de detecção remota, na banda do visível
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Advisor(s)
Abstract(s)
A fotografia aérea e as imagens de satélite são amplamente reconhecidas como uma fonte de
dados para produção de cartografia de áreas de grande extensão. A utilização de técnicas
fotogramétricas adequadas pode fornecer mapas representativos da geomorfologia de um
lugar e quantificação do movimento de massas (Kääb e Vollmer, 2000). Nas regiões com
permafrost, as deformações da camada activa visível em glaciares rochosos são induzidas
pelo clima, revelando-se assim, um geo-indicador-chave de mudanças ambientais. A
movimentação desses glaciares pode atingir velocidades à superfície, desde poucos
centímetros até alguns metros por ano, dependendo das propriedades do solo e das condições
térmicas. No continente Antárctico, as taxas de movimento de massa ainda são pouco
estudadas, especialmente na região da Península Antárctica, onde podem ser observados
glaciares rochosos em zonas livres de gelo (Ilhas Shetland do Sul). A capacidade actual de
medir movimentos de massa anteriores ao advento das tecnologias de posicionamento global
ou detecção remota, é possível, através da análise de colecções dos fotogramas existentes. O
objectivo deste estudo é medir os deslocamentos da camada activa do permafrost nas Ilhas
Shetland do Sul, com recurso a imagens de alta resolução (fotogramas e imagens de satélite -
banda visível) e através de técnicas fotogramétricas e de processamento digital de imagem.
Foram analisados vários fotogramas da década de 1950 da Península de Hurd (Ilha
Livingston) e comparados com imagens de satélite de 2010. Com base nos dois conjuntos de
dados foram produzidas imagens ortorrectificadas a partir das quais foram inferidos
movimentos de massa horizontais dos glaciares rochosos, na ordem dos decímetros por ano,
variando de acordo com a inclinação dos mesmos. O contraste das velocidades inferidas com
velocidades medidas recentemente por sistemas de posicionamento global em estacas assentes
em todo o glaciar rochoso forneceu perspectivas para uma evolução ambiental desta região.
Aerial photography and satellite images are widely recognized as a source of data for the production of maps of large areas of extension. The use of appropriate photogrammetric techniques can provide representative maps of the geomorphology of a place and through them the quantification of mass movement (Kääb & Vollmer, 2000). In mountain permafrost the active layer deformation visible in rock glaciers are induced by climate, revealing thus a geo-indicator of environmental modification. Changes in these glaciers can reach surface velocities from a few centimeters to a few meters per year, depending on soil properties and thermal conditions. In Antarctica, mass movement velocities are still little studied, especially in the Antarctic Peninsula region, where particularly in the ice free areas of the South Shetland Islands several rock glaciers can be identified. Today’s capability to measure mass movement previous to satellite based remote sensing and global navigation satellite systems is possible by re-analyzing available photogrammetric frames. This study’s objective is to measure the active layer of permafrost mass movement in the South Shetland Islands, made with the use of high-resolution images (frames and satellite images - visible band) and applying photogrammetry and digital image processing. Frames from the 1950’s of the Hurd Peninsula (Livingston Island) were analyzed and compared to 2010’s satellite images. From both data sets, orthorectified images were produced from which, horizontal mass movement of the rock glacier was inferred to a few decimeters per year, varying with the rock glacier steepness. Contrasting these inferred velocities with recently measured velocities by differential global positioning systems at staves deployed throughout the rock glacier provide an outlook to this region environmental evolution.
Aerial photography and satellite images are widely recognized as a source of data for the production of maps of large areas of extension. The use of appropriate photogrammetric techniques can provide representative maps of the geomorphology of a place and through them the quantification of mass movement (Kääb & Vollmer, 2000). In mountain permafrost the active layer deformation visible in rock glaciers are induced by climate, revealing thus a geo-indicator of environmental modification. Changes in these glaciers can reach surface velocities from a few centimeters to a few meters per year, depending on soil properties and thermal conditions. In Antarctica, mass movement velocities are still little studied, especially in the Antarctic Peninsula region, where particularly in the ice free areas of the South Shetland Islands several rock glaciers can be identified. Today’s capability to measure mass movement previous to satellite based remote sensing and global navigation satellite systems is possible by re-analyzing available photogrammetric frames. This study’s objective is to measure the active layer of permafrost mass movement in the South Shetland Islands, made with the use of high-resolution images (frames and satellite images - visible band) and applying photogrammetry and digital image processing. Frames from the 1950’s of the Hurd Peninsula (Livingston Island) were analyzed and compared to 2010’s satellite images. From both data sets, orthorectified images were produced from which, horizontal mass movement of the rock glacier was inferred to a few decimeters per year, varying with the rock glacier steepness. Contrasting these inferred velocities with recently measured velocities by differential global positioning systems at staves deployed throughout the rock glacier provide an outlook to this region environmental evolution.
Description
Dissertação de Mestrado, Geomática, Faculdade de Ciências e Tecnologia, Universidade do Algarve, 2015
Keywords
Permafrost Glaciar rochoso Fotogrametria Detecção remota Rock-glacier Photogrammetry Remote sensing