Improvements in 3-D digital mapping for geomorphological and Quaternary geological cartography

Abstract

Abstract. In recent decades, GIS tools have been directly applied to photo-interpretative geomorphological and geological mapping. Although these tools are powerful and effective tools in the creation of digital maps, it is often very difficult to obtain a correct recognition of the nature and boundaries of geomorphological landforms using two-dimensional images. In addition, the output typically requires some improvements, usually by means of field verifications or using oblique field photographs. The aim of this paper is to present the ArcGDS ™ tool, which allows the direct exploitation, visualization and digitization of stereoscopic digital linear scanned images (e.g. digital image strips, © swisstopo). Through two case studies, we show how 3-D digital mapping makes it possible to produce Quaternary geological and geomorphological maps with a limited complementary fieldwork approach and to provide a quantitative assessment of surface deformations through the acquisition of precise elevation coordinates. Combined with high-resolution digital elevation models, ArcGDS ™ is a powerful tool, particularly over large areas, as well as under forest cover and on very steep slopes.

Glacial lake outburst flood hazard assessment by satellite Earth observation in the Himalayas (Chomolhari area, Bhutan)

“…Detailed geomorphological mapping took place by combining three EO base maps and considering the pros and cons of every product. Direct mapping of geomorphological units was done on a VHRO KOMPSAT-2 orthophoto from 27 November 2010, with a ground resolution of 2 m. Shape reconnaissance was improved thanks to hillshades of TanDEM-X DEM, with absolute and relative vertical accuracies of 5 and 2 m (Ambrosi et al, 2018). The joint use of orthophotos and hillshaded DEMs for geomorphological mapping, as well as the differentiation of slope, slope foot, glacial, glaciofluvial and periglacial landforms and deposits, was done according to the recommendations of Ambrosi and Scapozza (2015).…”

“…PSI analysis was conducted only with the stacks of EN-VISAT ASAR images of the descending orbit and of ALOS-1 PALSAR-1 images of the ascending orbit, because for the other image stacks the number of acquisitions was not sufficient for this kind of processing. For details about satellite SAR acquisitions, processing and interpretation please refer to Ambrosi et al (2018). The complete set of images and data available for GLOF hazard assessment in the Chomolhari area is listed in Table 1.…”

“…Due to its extension, importance in the south-Asiatic geopolitical context and natural sensitivity to climate change, the Himalayas were recently of great interest in research projects related to landslide-(e.g. Ambrosi et al, 2018) and glacierrelated (e.g. Allen et al, 2016) hazard assessments, including morphological studies trying to quantify future lake formation by glacier melting (e.g.…”

“…This paper presents a GLOF hazard assessment for the supraglacial lake Wa-007 on the Thangothang Chhu glacier, Chomolhari area in the Bhutan Himalayas. This assessment was carried out in the framework of a European Space Agency-World Bank (ESA-WB) collaboration project on satellite EO in the Himalayas, where landslides, floods and GLOF hazard assessments were performed in Nepal and Bhutan (Sauerbier et al, 2015a;Scapozza, 2015;Ambrosi et al, 2018). Within this framework, the GLOF hazard assessment has made it possible to combine observations from flood and landslide hazard mapping, as well as to valorise the products derived from land use and land cover mapping and from the generation of high-resolution digital-elevation models (DEMs).…”

Introduction to the special issue of Geographica Helvetica: "Mapping, measuring and modeling in geomorphology"

“…Their work highlights the fact that the spatial heterogeneity of these relatively common features means that they can influence the surface hydrology in ways that can be both positive and negative. Ambrosi and Scapozza (2015) adopt a pioneering approach using the latest digital software to generate 3-D maps from scanned 2-D stereoscopic images. The outcome of their work has allowed them to quantitatively assess historical ground surface deformation on challenging mountainous terrain with unprecedented accuracy, and with a minimum of ground truthing.…”