Rapid viewshed analyses: A case study with visibilities limited by trees and buildings

Abstract

High-resolution digital surface models improve the precision of viewshed analyses, but these data can be challenging to use for large study areas. We developed a 2D viewshed (2DView) approach, that uses land cover to estimate viewshed extent. We aimed to develop a practical approach to map viewing areas for >1000 waterbodies spread over 6000 km2. In this paper, we present a case study in which we use the 2DView method for a viewshed analysis where trees and buildings, rather than terrain, are the primary obstacles to visibility. We evaluate the 2DView through comparison with DSM-based viewsheds.We used 30 waterbodies for our evaluation. We applied our 2DView analysis using high-resolution (i.e. 1 m) land cover and building footprint data to represent trees and buildings, respectively. For conventional 3DView, we used 1) true digital surface models and 2) bare-earth elevation models modified by adding fixed heights (i.e. 30 m) for trees and buildings. The 2DView method had good agreement with the 3DView method with average intersection-of-unions ranging from 90 to 95%. The 2DView method tends to overestimate viewshed extents; thus, it can serve as a pre-screening tool to reduce the instances when more accurate 3DView analyses are required.