Abstract
We compared three methods for deriving communication viewsheds, which indicate the coverage areas for transmitter points from high-resolution digital surface models. Communication viewsheds were analyzed with a novel 3D Fresnel zone method, as well as line-of-sight (LOS) analysis and 2D Fresnel zone analysis, using high-resolution digital surface models (DSM) from a topographical survey. A LOS analysis calculates a visibility index by comparing the profile elevations of landforms between the transmitter and the receiver, using LOS elevations. A 2D Fresnel zone analysis calculates a 2D Fresnel index by comparing the profile elevations of landforms with the transverse plane elevations of the Fresnel zone. A 3D Fresnel zone analysis quantitatively analyzes communication stability by calculating a 3D Fresnel index, obtained by comparing the elevations of every terrain cell in a Fresnel zone with the total altitude of the Fresnel zone. The latter produced the most accurate results. Indexes derived by applying different transmitter offset heights, signal frequencies, and DSM resolutions for each of the three methods were then quantitatively analyzed. As both the offset height of the transmitter and the signal frequency decreased, the differences between the results derived from each method increased significantly. Moreover, larger DSM cells generated less accurate results.
Highlights
Viewshed analysis is a representative method for spatial analysis that identifies the visibility of every point on a terrain surface from any observation point and marks the viewsheds on a raster image [1]
The input geographic data used for a viewshed analysis include digital elevation models (DEMs) [5,6] or triangulated irregular networks (TINs) [7,8,9]
This study compared the performance of LOS analysis, 2D Fresnel zone analysis, and 3D Fresnel zone analysis for extracting communication viewsheds from high-resolution topographic data
Summary
Viewshed analysis is a representative method for spatial analysis that identifies the visibility of every point on a terrain surface from any observation point and marks the viewsheds on a raster image [1]. A 2D Fresnel zone analysis calculates the transverse cross-sectional altitude of the Fresnel zone, formed between the transmitter cell and the receiver cell, and extracts the terrain profile altitude between the two points to account for obstacles within the zone. These two altitudes are compared to evaluate the possibility of communication in a binary mode (either possible or impossible). Like a LOS analysis, the 2D Fresnel zone analysis extracts every point contacting the xy coordinate grid using the LOS between the current transmitter cell and the current receiver cell (Figure 4d). According to the three analysis methods, the visibility index map, 2D Fresnel index map, and 3D Fresnel index map are stored, and the number of index maps is equal to that of transmitter cells
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