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The queensway of New York city. A proposal for sustainable mobility in queens
Published in Michèle Pezzagno, Maurizio Tira, Town and Infrastructure Planning for Safety and Urban Quality, 2018
C. Ignaccolo, N. Giuffrida, V. Torrisi
This viewshed analysis (Fig. 7) shows which areas are visible from a specific location. View-shed analysis was performed putting some points on the railroad as observation points. The raster is a DSM (DEM + building eights). The result shows that the future project would guarantee the privacy of people who live nearby the QueensWay infrastructure (especially in the Southern part) and, in the same moment, the QueensWay would offer great views of the Forest Park. Fig. 8 shows that QueensWay would be a great link between the built area of Southern Queens and the Forest Park which is not easily accessible nowadays. In addiction a lot of students could use the QueensWay as daily path to reach their schools or other public facilities. In this way there will be also a decrease of traffic congestion, because a lot of commercial buildings are located nearby the former railroad. Last but not least QueensWay could connect two areas of Queens with different Medium Age. The park would be easily reached by Metro thanks to 5 stops (1 in the Northern part, 2 in the middle, 2 in the Southern part) located within a distance of 300 m from the former railroad (Fig. 9). QueensWay would be the only N-S link between the metro stops which are on 3 different lines.
Latest High-Resolution Remote Sensing and Visibility Analysis for Smart Environment Design
Published in Prasad S. Thenkabail, Remote Sensing Handbook, 2015
Yoshiki Yamagata, Daisuke Murakami, Hajime Seya
On the other hand, some other indexes examine visibility of each cell in a 3D raster, just like the viewshed analysis. This type of indexes has been discussed extensively; particularly, after the 3D analyst toolbox, a collection of 3D spatial analysis tools including viewshed analysis tools, was installed in ArcGIS (ESRI Inc.) in 1998 (Ma, 2003). Table 24.2 summarizes such viewshed-oriented indexes. The standard viewshed examines whether each cell is visible or not from an observation point. The cumulative viewshed and the total viewshed (Wheatley, 1995; Llibera, 2003) accumulate standard viewsheds from each observation point and provide a raster of recoding in each cell the number of observation points visible. The difference between the two indexes is that the former assumes a set of selected sites as observation points, while the latter assumes observation points being distributed all over the target region. On the other hand, viewshed-oriented (or raster-based) index was also proposed in the context of the isovist analysis. Isovisi-matrix (Morello and Ratti, 2009) is such an index. It provides a 3D raster map whose cells are colored according to the number of cells in the raster that are visible from the cell. From a viewpoint of viewshed analysis, this index appears to be essentially identical to the total viewshed.
The representativeness and spatial bias of volunteered geographic information: a review
Published in Annals of GIS, 2018
If detailed information on sampling or observation effort is available, such information can then be incorporated to correct for spatial bias. Zhu et al. (2015) proposed an approach for predictive mapping using VGI (e.g. mapping wildlife habitat suitability based on wildlife sighting records elicited from the local residents). When extracting the suitability-environment relationships from VGI records, they developed a method to correct for spatial bias in VGI by inversely weighting VGI observations with weights proportional to the cumulative visibility at the observation sites. Here ‘cumulative visibility’ is the frequency of a given location being seen by observers from the routes taken by the local residents, which is calculated using viewshed analysis based on the routes and a digital elevation model of the study area. It is used as a proxy of the underlying observation effort of the local residents in observing the wildlife.