Shadow: R package for geometric shadow calculations in an urban environment

Abstract

This paper introduces the shadow package for R. The package provides functions for shadowrelated calculations in the urban environment, namely shadow height, shadow footprint and Sky View Factor (SVF) calculations, as well as a wrapper function to estimate solar radiation while taking shadow effects into account. All functions operate on a layer of polygons with a height attribute, also known as "extruded polygons" or 2.5D vector data. Such data are associated with accuracy limitations in representing urban environments. However, unlike 3D models, polygonal layers of building outlines along with their height are abundantly available and their processing does not require specialized closed-source 3D software. The present package thus brings spatio-temporal shadow, SVF and solar radiation calculation capabilities to the open-source spatial analysis workflow in R. Package functionality is demonstrated using small reproducible examples for each function. Wider potential use cases include urban environment applications such as evaluation of micro-climatic influence for urban planning, studying urban climatic comfort and estimating photovoltaic energy production potential.