Papers by Leonhard Blesius
Geomorphology, Jul 1, 2007
Landslide susceptibility maps can be prepared in a variety of ways. Many geoscientists favour the... more Landslide susceptibility maps can be prepared in a variety of ways. Many geoscientists favour the use of an overlay model approach in which several map layers are combined by some arithmetic rules to determine the potential for sliding in an area or region. The resulting susceptibility maps, although based on a subjective weighting of relevant factors, can often be of high accuracy and utility. In order to obtain the relevant input data for this type of analysis, remotely sensed data are often used. To date, susceptibility mapping, just as the mapping of historic and individual landslides, has tended to require higher-resolution imagery. This has somewhat limited the application of landslide susceptibility mapping. While high-resolution air photo or satellite imagery is superior to lower resolution imagery for the purpose of mapping of historic and individual landslides, such higher levels of resolution may not be required for the development of landslide susceptibility maps. In order to determine if medium-resolution satellite imagery, such as SPOT or ASTER, could provide the needed data for landslide susceptibility mapping, a comparison was undertaken of landslide susceptibility model output resulting from the use of stereo NAPP aerial photography versus the use of data obtained from stereo SPOT imagery. The test area selected for this study consisted of two watersheds, Pena Canyon and Big Rock Canyon, situated west of Santa Monica, California, USA, along the Pacific Coast Highway. Both watersheds have a long and well-documented history of landslide activity and sufficient geologic variability and complexity to provide a good test site. The specific overlay model used in this evaluation required input data consistent with the needs of many other models of this type. The model output derived from the two different data sources and presented here in the form of susceptibility maps were virtually identical. Statistical and difference analysis confirmed that both methods of obtaining input data provide similar results and successfully identified landslide prone areas. These results suggest that satellite imagery, in this instance, SPOT images, could potentially be used in lieu of conventional air photos, to evaluate landslide susceptibility. In many situations, especially in the case of remote locations and/or developing countries, this capability should result in substantial savings in terms of time, financial resources, and overall viability.
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International Journal of Remote Sensing, Sep 10, 2005
ABSTRACT Land‐cover classifications in mountainous terrain are often hampered by the topographic ... more ABSTRACT Land‐cover classifications in mountainous terrain are often hampered by the topographic effect. Several strategies can be pursued to correct for this. A traditional approach is to use training areas for the same land‐cover class for different topographic positions and later merge those into one class. Other solutions involve topographic corrections, such as a Minnaert correction. In this study the classification result of the traditional training‐area approach was compared with the classification result of a Minnaert‐corrected image. In order to derive the Minnaert constants, a SPOT XS scene of the Santa Monica Mountains, USA, was divided into three visually relatively homogeneous regions. Eighty per cent of the pixels were assigned the same land cover in both classifications. Differences in classification were mainly in the section of the image that had more diverse land cover than in the more homogeneous chaparral‐covered eastern section. This supports previous findings that the Minnaert constant needs to be derived for individual land‐cover classes. The findings also suggest that after the Minnaert correction the resulting classification is comparable to the classification obtained using a more traditional approach.
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Remote Sensing, 2016
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Entropy, 2015
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High resolution satellite and aerial imagery of fluvial systems contain much information about pl... more High resolution satellite and aerial imagery of fluvial systems contain much information about planform river channel features. However, not much is known about how these forms quantitatively related to river channel process, specifically, discharge. This research explores methods for remote image-based river discharge estimation through Object-Based Image Processing (OBIA) and GIS techniques. Previous efforts in image-based discharge estimation have relied primarily on manual delineation of river features and the input of reach-averaged values of these features into statistically based models for estimation. In addition to analyzing OBIA techniques for channel feature delineation and measurement, this approach investigates techniques of discharge estimation model design, validation, and correction along a reach, utilizing variation in ``standard'' channel features (e.g. water surface width), along with less tangible channel feature metrics derived from OBIA. Rather than pre...
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In order to mitigate hazards of mass failure, the first step is the identification of potentially... more In order to mitigate hazards of mass failure, the first step is the identification of potentially unstable slopes, resulting in a landslide susceptibility map. Satellite imagery is an important component in the derivation of critical parameters. Susceptibility maps can be constructed in a variety of ways, including multivariate statistics, heuristic models, and geotechnical models. Each method has been shown to successfully identify hazardous slopes. The method employing geotechnical data has attracted attention, but the problem is a lack of critical parameters such as angle of internal friction or cohesion. These data may be available for few selected slopes, but typically not over a spatially coherent area. This severely limits the use of geotechnical models for landslide susceptibility maps. This study addresses the potential of using remote sensing and in particular high-resolution satellite imagery to derive values for important variables such as angle of internal friction and ...
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Clouds and other aerosols greatly alter the nature of the surface radiation budget, particularly ... more Clouds and other aerosols greatly alter the nature of the surface radiation budget, particularly in reducing the quantity and changing the quality of solar radiation incident upon the surface as well as enhancing down welling longwave radiation. This study aims to characterize the surface radiation budget regime in southwest San Francisco, CA, USA, and in particular to examine the radiative control and signature of the ubiquitous coastal Californian fog. Direct and diffuse solar radiation and thermal infrared radiation data were recorded at a monitoring station at San Francisco State University at 15-minute intervals over the period June 2005 to August 2008. Indices are developed to characterize the radiation signatures of different atmospheric conditions, principally summer advection fog, winter frontal clouds, air pollution and smoke. The resulting surface radiation budget produces a distinctive seasonal radiation regime that is unique to the narrow coastal strip, producing striki...
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International Journal of Remote Sensing, 2005
ABSTRACT Land‐cover classifications in mountainous terrain are often hampered by the topographic ... more ABSTRACT Land‐cover classifications in mountainous terrain are often hampered by the topographic effect. Several strategies can be pursued to correct for this. A traditional approach is to use training areas for the same land‐cover class for different topographic positions and later merge those into one class. Other solutions involve topographic corrections, such as a Minnaert correction. In this study the classification result of the traditional training‐area approach was compared with the classification result of a Minnaert‐corrected image. In order to derive the Minnaert constants, a SPOT XS scene of the Santa Monica Mountains, USA, was divided into three visually relatively homogeneous regions. Eighty per cent of the pixels were assigned the same land cover in both classifications. Differences in classification were mainly in the section of the image that had more diverse land cover than in the more homogeneous chaparral‐covered eastern section. This supports previous findings that the Minnaert constant needs to be derived for individual land‐cover classes. The findings also suggest that after the Minnaert correction the resulting classification is comparable to the classification obtained using a more traditional approach.
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Global and Planetary Change, 2011
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Geomorphology, 2007
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Cartography and Geographic Information Science, 2010
... This methodology was tested on a section of the Santa Monica Mountains near Malibu, Californi... more ... This methodology was tested on a section of the Santa Monica Mountains near Malibu, California. ... studies are: Shu-Quiang and Unwin (1992), Reading (1993), Hearn (1995), Anbalagan and Singh (1996), Gupta and Anbalagan (1997), Hylland and Lowe (1997), Pachauri et al. ...
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Remote Sensing, 2014
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Papers by Leonhard Blesius