Calculating the inherent visual structure of a landscape (inherent viewshed) using high-throughput computing

This paper describes a method of calculating the inherent visibility at all locations in a landscape (‘total viewshed’) by making use of redundant computer cycles. This approach uses a simplified viewshed program that is suitable for use within a distributed environment, in this case managed by the Condor system. Distributing the calculation in this way reduced the calculation time of our example from an estimated 34 days to slightly over 25 hours using a cluster of 43 workstations. Finally, we discuss the example ‘total viewshed’ raster for the Avebury region, and briefly highlight some of its implications

Fracking in Pennsylvania: A Spatial Analysis of Impacts on Land Cover and Land Use, the Viewshed, and the Audioshed

Hydraulic fracturing is the process of extracting natural gas from layers of shale rock beneath the surface of the Earth. The largest source of natural gas in the US is the Marcellus Shale, largely located in Pennsylvania, and it is believed to hold about 141 trillion cubic feet of natural gas in its shale deposits. My study examined the impacts of well sites on land cover and land use, the viewshed, and the audioshed. To study the effect of wellpads on land use and land cover, we overlaid a layer of wellpads over land cover data as well as a layer of Pennsylvania natural resources. To study the visual and sound impacts of wellpads and compressor stations, we generated viewsheds and audiosheds and then calculated the percent of land, road, and trails impacted within different environment types. We found that the majority of producing wells are currently found in forested areas and within 1320 feet of a stream or wetland. However, we found that there is also seemingly a bias against placing wellpads near wetland areas. Additionally, rural land cover areas were found to have a disproportionate number of wellpads in relation to their area within the Marcellus shale region. Rural environments were also found to be impacted the highest in regards to the viewshed, having over 20% of the tile within the fracking viewshed for tiles with at least 2 wellpads. In regards to noise impacts, high road density areas and state forest areas were found to have similar percentages within the audioshed for tiles with at least one compressor station. So overall, in areas with at least 2 wellpads, rural areas have the most potential impacts due to fracking for both land cover and land use as well as the viewshed

Exploring multiple viewshed analysis using terrain features and optimisation techniques

The calculation of viewsheds is a routine operation in geographic information systems and is used in a wide range of applications. Many of these involve the siting of features, such as radio masts, which are part of a network and yet the selection of sites is normally done separately for each feature. The selection of a series of locations which collectively maximise the visual coverage of an area is a combinatorial problem and as such cannot be directly solved except for trivial cases. In this paper, two strategies for tackling this problem are explored. The first is to restrict the search to key topographic points in the landscape such as peaks, pits and passes. The second is to use heuristics which have been applied to other maximal coverage spatial problems such as location-allocation. The results show that the use of these two strategies results in a reduction of the computing time necessary by two orders of magnitude, but at the cost of a loss of 10% in the area viewed. Three different heuristics were used, of which Simulated Annealing produced the best results. However the improvement over a much simpler fast-descent swap heuristic was very slight, but at the cost of greatly increased running times. © 2004 Elsevier Ltd. All rights reserved

Calculating the inherent visual structure of a landscape ('total viewshed') using high-throughput computing

This paper describes a method of calculating the inherent visibility at all locations in a landscape (‘total viewshed’) by making use of redundant computer cycles. This approach uses a simplified viewshed program that is suitable for use within a distributed environment, in this case managed by the Condor system. Distributing the calculation in this way reduced the calculation time of our example from an estimated 34 days to slightly over 25 hours using a cluster of 43 workstations. Finally, we discuss the example ‘total viewshed’ raster for the Avebury region, and briefly highlight some of its implications

Siting Multiple Observers for Maximum Coverage: An Accurate Approach

The selection of the minimal number of observers that ensures the maximum visual coverage over an area represented by a digital elevation model (DEM) have great interest in many elds, e.g., telecommunications, environment planning, among others. However, this problem is complex and intractable when the number of points of the DEM is relatively high. This complexity is due to three issues: 1) the di culty in determining the visibility of the terrain from one point, 2) the need to know the visibility at all points of the terrain and 3) the combinatorial complexity of the selection of observers. The recent progress in total-viewshed maps computation not only provides an e cient solu- tion to the rst two problems, but also opens other ways to new solutions that were unthinkable previously. This paper presents a new type of cartography, called the masked total viewshed map, and provides optimal solutions for both sequential and simultaneous observers location.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Visibility graphs and landscape visibility analysis

Visibility analysis based on viewsheds is one of the most frequently used GIS analysis tools. In this paper we present an approach to visibility analysis based on the visibility graph. A visibility graph records the pattern of mutual visibility relations in a landscape, and provides a convenient way of storing and further analysing the results of multiple viewshed analyses for a particular landscape region. We describe how a visibility graph may be calculated for a landscape. We then give examples, which include the interactive exploration ofa landscape, and the calculation of new measures of a landscape?s visual properties based on graph metrics ? in particular, neighbourhood clustering coefficient and path length analysis. These analyses suggest that measures derived from the visibility graph may be of particular relevance to the growing interest in quantifying the perceptual characteristics of landscapes

Ecological Effects of Fear: How Spatiotemporal Heterogeneity in Predation Risk Influences Mule Deer Access to Forage in a Sky‐Island System

Forage availability and predation risk interact to affect habitat use of ungulates across many biomes. Within sky‐island habitats of the Mojave Desert, increased availability of diverse forage and cover may provide ungulates with unique opportunities to extend nutrient uptake and/or to mitigate predation risk. We addressed whether habitat use and foraging patterns of female mule deer (Odocoileus hemionus) responded to normalized difference vegetation index (NDVI), NDVI rate of change (green‐up), or the occurrence of cougars (Puma concolor). Female mule deer used available green‐up primarily in spring, although growing vegetation was available during other seasons. Mule deer and cougar shared similar habitat all year, and our models indicated cougars had a consistent, negative effect on mule deer access to growing vegetation, particularly in summer when cougar occurrence became concentrated at higher elevations. A seemingly late parturition date coincided with diminishing NDVI during the lactation period. Sky‐island populations, rarely studied, provide the opportunity to determine how mule deer respond to growing foliage along steep elevation and vegetation gradients when trapped with their predators and seasonally limited by aridity. Our findings indicate that fear of predation may restrict access to the forage resources found in sky islands

Hide and Seek. Roads, Lookouts and Directional Visibility Cones in Central Anatolia

In Cappadocia (central Turkey), routes that were only of a secondary importance during the Roman age acquired a new relevance starting from the end of the 7th century. In this framework, to what extent did the archaeological evidence match the picture recalled by the written sources? To address this question, the relationship between movement and visibility was considered and viewshed analyses were conducted from targeted and strategic spots set along the routes considered. This allowed to better understand the role and the different functions of those axes crossing Cappadocia, and to evaluate the Byzantine/Arab military strategies in central Anatolia