SkyHelios – GPU-based sky view factor and sunshine duration model

About the model

SkyHelios uses modern graphics hardware as a general-purpose vector computer to calculate the continuous sky view factor for every point in a complex area, based on a digital elevation model, urban obstacles or other digital input files. Using the graphics processor keeps computing time short, development time short, and costs low through the use of open-source frameworks. Various raster and vector data formats can be imported and processed, and results can be visualized directly on screen, stored and exported. SkyHelios can be seen as a further development of the RayMan model, and results can be interlinked with RayMan Pro for the calculation of mean radiant temperature and thermal indices.

The sky view factor describes how much of the sky hemisphere is visible from a point. Schematic.

Input data are processed on the GPU; results are stored and exported. Schematic.

Sunshine duration follows from the sun path and the obstacles along it. Schematic.

Supported data formats

Raster files

GDAL formats, e.g. GeoTiff (*.tif)
Tab-delimited text files (*.tab)
CSV files (*.csv)
Text files (*.txt)
ASCII grid (*.asc)
Portable network graphics (*.png)

Vector files

CityGML (*.gml, *.xml)
RayMan obstacle files (*.obs)
OGR formats, e.g. shapefiles (*.shp)
Collada meshes (*.dae)

Application and use areas

Application

Applied and urban climatology
Sky view factor and shading analysis
Solar access and sunshine duration studies
Combined with RayMan Pro for thermal comfort assessment

Uses

Education and teaching
Academic research
Urban and regional planning support

Related model and outlook

For thermal indices (PET, PMV, SET*) at a single location, see RayMan Pro. SkyHelios supplies the spatial fields; RayMan Pro turns them into thermal comfort assessments.

SkyHelios is the platform for new developments of the RayMan model family.
Work is ongoing on the spatial estimation of thermal indices and on additional input and output formats.

Selected publications

Matzarakis, A., Matuschek, O., 2011: Sky View Factor as a parameter in applied climatology – rapid estimation by the SkyHelios model. Meteorologische Zeitschrift 20, 39–45. doi:10.1127/0941-2948/2011/0499 →
Fröhlich, D., Matzarakis, A., 2018: Spatial Estimation of Thermal Indices in Urban Areas – Basics of the SkyHelios Model. Atmosphere 9, 209, 1–14. doi:10.3390/atmos9060209 →
Fröhlich, D., Gangwisch, M., Matzarakis, A., 2019: Effect of radiation and wind on thermal comfort in urban environments – application of the RayMan and SkyHelios model. Urban Climate 27, 1–7. Read on ScienceDirect →
Matzarakis, A., Gangwisch, M., Fröhlich, D., 2021: RayMan and SkyHelios Model. In: Palme, M., Salvati, A. (eds) Urban Microclimate Modelling for Comfort and Energy Studies. Springer, Cham, 339–361. doi:10.1007/978-3-030-65421-4_16 →
Matuschek, O., Matzarakis, A., 2010: Estimation of sky view factor in complex environment as a tool for applied climatological studies. In: Matzarakis, A., Mayer, H., Chmielewski, F.-M. (Eds.), Proceedings of the 7th Conference on Biometeorology. Ber. Meteorol. Inst. Univ. Freiburg No. 20, 535–540.

Request SkyHelios

SkyHelios is available free of charge. Please register using the form below – you will then receive the download link by email from Prof. Matzarakis.

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Or write directly to: andreas.matzarakis@meteo.uni-freiburg.de