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Topographic mapping of the volcano Nevado Ojos del Salado using optical and microwave image data
Titel:
Topographic mapping of the volcano Nevado Ojos del Salado using optical and microwave image data
Auteur:
Kaufmann, Viktor
Verschenen in:
Geocarto international
Paginering:
Jaargang 13 (1998) nr. 2 pagina's 53-64
Jaar:
1998-06
Inhoud:
The area of interest is located at the border between Chile and Argentina at 27°10' S. latitude and 68°30' W. longitude in the High Cordillera of the Andes and includes the second-highest mountain of America, the Nevado Ojos del Salado. Although the official Chilean altitude is given as 6,880 m, other figures can be found in the literature and various other maps. Situated in a picturesque volcanic terrain rising above the Puna de Atacama, Nevado Ojos del Salado is not only interesting from a geomorphological point of view, it is, e.g., the world's highest volcano, but also has recently become a much-favored destination of the mountaineering world. Unfortunately, this area is not covered by reliable and publicly available maps at scales larger than 1:250,000. Therefore, this paper describes the methods employed in and results obtained from topographic mapping of this remote area using spaceborne as well as airborne remotely sensed data. Exploiting Space Shuttle Earth-viewing photographs, ERS-1 Synthetic Aperture Radar images, and aerial photographs, it was intended to derive orthophotos, digital elevation models, topographic/geomorphological base maps, including various derivatives, such as anaglyphs, stereograms, and axonometric views, respectively, at a minimum of costs. In order to get a general overview, i.e. to generate a base map of the area, stereoscopic hand-held photographs from NASA's SSEOP database were used. Parallax-free stereo vision was achieved by means of an analytical plotter. Ground control points were taken from the existing Chilean maps at scales 1:250,000 and 1:500,000 in order to georeference the image content. A digital orthophoto and a topographic base map at 1:400,000 are presented. Furthermore, two overlapping same-side ERS-1 SAR images from adjacent descending orbits were acquired and provided in digital format by the European Space Agency. In a first step, the image data was radiometrically enhanced, and proper radar stereograms were generated for image interpretation purposes. This is followed by a brief discussion of recently developed mapping methods for radar images. In order to facilitate large-scale mapping a strip of panchromatic aerial photographs at 1:30,000 scale, provided by the Instituto Geografico Militar de Chile, was photogrammetrically oriented using ground control points measured in one of the Shuttle stereopairs at 1:840,000 scale. As a result, a topographic map at 1:15,000 scale and a high-resolution digital elevation model of the central part of the Nevado Ojos del Salado were generated. The photographs, given as analog paper prints, were scanned and thereafter digitally rectified and mosaicked to form an orthophoto of the volcano Ojos del Salado. A stereomate of this orthophoto was produced as well. The scope of this work also includes various combined image-line maps. The presented cartographic products, available either in analog or in digital format, for the first time allow detailed geomorphological mapping of the Nevado Ojos del Saldo and its surroundings and provide a far better means of orientation for mountaineers in this very remote and deserted area in the Andes.
Uitgever:
Taylor & Francis
Bronbestand:
Elektronische Wetenschappelijke Tijdschriften
Details van artikel 239 van 250 gevonden artikelen
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