GIS-based Spatial Viewshed Analysis of Cableway Construction Projects in Scenic Areas

GIS and GPS are used for the quantitative analysis of visual landscape impact of the old and new Cloud Valley Cableway in the Yellow Mountain.The results show that viewshed,quantity of visible sensitive scenic areas,and visible length from the tour routes of the new cableway are much smaller than those of the old one,so the new cableway has limited impact on visual landscapes of the scenic area,and basically meets the requirement of not damaging natural landscape features of the Yellow Mountain.GIS-and GPS-based spatial viewshed analysis methods have promising prospects in researches on landscape infl uence of scenic areas,and both of them are also signifi cant technical supports for the environmental protection verifi cation of construction projects in scenic areas.

Parallel algorithm for viewshed analysis on a modern GPU

Spatial analysis,including viewshed analysis,is an important aspect of the Digital Earth system.Viewshed analysis is usually performed on a large scale,so efficiency is important in any Digital Earth application making these calculations.In this paper,a real-time algorithm for viewshed analysis in 3D scenes is presented by using the parallel computing capabilities of a graphics processing unit(GPU).In contrast to traditional algorithms based on line-of-sight,this algorithm runs completely within the programmable 3D visualization pipeline to render 3D terrains with viewshed analysis.The most important difference is its integration of the viewshed calculation with the rendering module.Invisible areas are rendered as shadows in the 3D scene.The algorithm process is paralleled by rasterizer units in the graphics card and by vertex and pixel shaders executed on the GPU.We have implemented this method in our 3D Digital Earth system with the DirectX 9.0c API and tested on some consumer-level PC platforms with interactive framerates and high image quality.Our algorithm has been widely used in related systems based on Digital Earth.

The topological viewshed:embedding topological pointers into digital terrain models to improve GIS capability for visual landscape analysis

The effort to develop a Digital Earth has made dramatic progress in terms of visualisation and visual data integration for use-cases which demand semantically rich analysis.To provide this analysis and ensure legitimate representations of the spatial data from which visualisation are derived,it is necessary to provide more comprehensive analytical capabilities of the view.Questions of aesthetic valuation of landscape require a richer analytical response than simply‘whether and possibly how much of’an object or area of land can be seen.It requires interrogation of the scene as it appears and to distinguish between transient visual effects and those locally invariant to view point change.This paper explores a data structure to support scene analytics.As such,it first reviews the existing techniques from the fields of GIS and computer graphics as to their potential and limitations in providing a qualitatively more nuanced visual analysis.It then introduces a new method of encoding visually apparent relationships into terrain models.A prototype implementation is presented based on the Quad-Edge Triangular Irregular Network,though it is believed that raster or vector implementation would be possible.Although developed primarily with landscape analysis in mind,the method could have wider applicability.

Reconstruction Design of Zaozhuang Gangue Hill Based on the Interaction of“Scenery”and“View”

Gangue hill is the associated accumulation landscape of long-term coal mining.There are a large number of gangue hills left in coal mining cities,which not only causes ecological damage but also affects the urban environment,thus becoming the focus of urban landscape transformation of coal mining cities.With the increase of people’s demand for ecological leisure,it has become the first choice to transform gangue hill and its surrounding areas into community parks.From the perspective of urban space and landscape system,as a huge regeneration landform in the city and a unique landscape in the mining area,gangue hill not only needs to be afforested,but also needs to be connected with mining heritages and landscape nodes in the city to form the interaction between“scenery”and“view”,so as to form an integrated mining cultural landscape system at the urban level.On the basis of this concept,taking the gangue hill of Zhongxing in Zaozhuang City as an example,this paper quantitatively analyzes the best landscape construction site in the gangue hill via viewshed analysis in GIS.Through this method,the gangue hill and Zhongxing mining heritage are closely combined,so as to establish the interactive relationship between“scenery”and“view”.It can guide the planning and design of sightseeing route and footpath system,and also provide a technical support for the design of community parks transformed from gangue hills.

Geospatial Model as Strategy to Prevent Forest Fires: A Case Study

The forests of the State of Durango have been severely affected by fires in recent years. Early detection of fires through watchtowers is essential. In this work a geospatial model was generated to optimize strategic visualization points, using a GIS environment. Analysis of the area of visibility was developed by integrating a digital model of elevation and a plant cover map. The resulting distribution generates more than 50% coverage of the studied area, in points that were not always the highest. It was concluded that this strategy would permit to increase the efficiency, mainly favoring the communities of pine, whose economic importance would justify the required investment.

A Comparative Study of Digital Terrain Data for Visibility Analysis in the Planning and Management of Scenic Resources

A DEM （digital elevation model） was once used to calculate viewsheds in the early days of GIS applications. The emergence of LiDAR （light detection and ranging） data which are likely to have higher spatial resolutions than traditional DEMs contributed to the improvements of calculation accuracy greatly. The objective of this study is to validate that the LiDAR data calculate and predict a viewshed better than the traditional low-resolution DEMs with 10 m and 30 m spatial resolutions. Using digital terrain data acquired for part of the Nez Perce National Forest in Idaho, calculation accuracy for viewsheds was scrutinized in depth. Four hundred and eighty four （484） observation points were selected randomly to compute viewsheds from the 1-m pixel, bare-earth LiDAR data and from the traditional 10 m and 30 m DEMs. The comparison of their RMSEs （root-mean-squared-error） values proves the newer generation of digital terrain data produces more accurate viewsheds than ones generated from the traditional DEMs. Analyses of variance and t-tests show the viewsheds calculated from various terrain models are statistically different. Therefore, findings from this study suggest that high-quality LiDAR data, if available, should be used for decision-making in planning for and the management of the scenic resources.

Deriving a minimum set of viewpoints for maximum coverage over any given digital elevation model data

This paper introduces how to automatically derive a minimum set of viewpoints for maximum coverage over a large scale of digital terrain data.This is a typical data and computation-intensive research covering a series of geocomputation tasks that have not been implemented efficiently or optimally in prior works.This paper introduces a three-step computational solution to resolve the problem.For any given digital elevation model(DEM)data,automatic generation of control viewpoints is the first step through map algebra calculation and hydrological modeling approaches.For each viewpoint,the viewshed calculation then has to be implemented.The combined viewshed derived from the viewshed of all viewpoints establishes the maximum viewshed coverage of the given DEM.Finally,detecting the minimum set of viewpoints for the maximum coverage is a Non-deterministic Polynomial-time hard problem.The outcome of the computation has broader societal impacts since the research questions and solutions can be adapted into realworld application and decision-making practice,such as the distribution,optimization and management of telecommunication infrastructure and wildfire observation towers,and military tactics and operations dependent upon landscape and terrain features.

Territorial Resilience Through Visibility Analysis for Immediate Detection of Wildfires Integrating Fire Susceptibility,Geographical Features,and Optimization Methods

Climate change effects tend to reinforce the frequency and severity of wildfires worldwide,and early detection of wildfire events is considered of crucial importance.The primary aim of this study was the spatial optimization of fire resources(that is,watchtowers)considering the interplay of geographical features(that is,simulated burn probability to delimit fire vulnerability;topography effects;and accessibility to candidate watchtower locations)and geo-optimization techniques(exact programming methods)to find both an effective and financially feasible solution in terms of visibility coverage in Chalkidiki Prefecture of northern Greece.The integration of all geographical features through the Analytical Hierarchy Process indicated the most appropriate territory for the installment of watchtowers.Terrain analysis guaranteed the independence and proximity of location options(applying spatial systematic sampling to avoid first order redundancy)across the ridges.The conjunction of the above processes yielded 654 candidate watchtower positions in 151,890 ha of forests.The algorithm was designed to maximize the joint visible area and simultaneously minimize the number of candidate locations and overlapping effects(avoiding second order redundancy).The results indicate four differentiated location options in the study area:(1)75locations can cover 90%of the forests(maximum visible area);(2)47 locations can cover 85%of the forests;(3)31locations can cover 80.2%of the forests;and(4)16 locations can cover 70.6%of the forests.The last option is an e fficient solution because it covers about 71%of the forests with just half the number of watchtowers that would be required for the third option with only about 10%additional forest coverage.However,the final choice of any location scheme is subject to agency priorities and their respective financial flexibility.