HORAYZON v1.2: an efficient and flexible ray-tracing algorithm to compute horizon and sky view factor

Abstract. Terrain parameters like topographic horizon and sky view factor (SVF) are used in numerous fields applications. In atmospheric climate modelling, such utilised to parameterise the effect of terrain geometry on radiation exchanges between surface atmosphere. Ideally, these derived from a high-resolution digital elevation model (DEM) because inferring them coarser data induces smoothing effect. Computing with conventional algorithms, however, is slow large amounts non-local have be processed. We propose new more efficient method, which based high-performance ray-tracing library. The algorithm can speed up calculation by 2 orders magnitude relative approach. By applying simplification remote topography, ray-tracing-based also applied very (<5 m) DEM data, would otherwise induce an excessive memory footprint. accompanied SVF algorithm, was verified work accurately for all – even steep complex terrain. compare computational performance accuracy two reference methods literature illustrate its benefits. Finally, we how sub-grid values efficiently computed newly wide range target grid resolutions (1–25 km).