A GIS tool to increase the visual quality of relief shading by automatically changing the light direction

Shaded relief representations were traditionally produced manually by specifically trained cartographers. This was however a labour-intensive and time-consuming task, which gave rise to numerous attempts of automation.Nowadays, many GIS applications implement hillshading using an oblique light source. This has standardised the method, providing a simple way to obtain reliable and consistent results. Its visual quality is however well below the standards of manual shading, where multiple light sources are employed to achieve a superior visual quality.In this work we present a GIS tool to enhance the visual quality of hillshading. We developed a technique to illuminate the landscape from two different angles and correct the tone according to either elevation or slope. With this method the quality of the shaded relief is superior to the standard method, but its level of automation and standardisation guarantees consistent and reproducible results. This method has been embedded into an ArcGIS toolbox.