Sky-View Factor as a Relief Visualization Technique

TLDR

Remote sensing provides the primary data for digital elevation models, which are visualized mainly by hill‑shading, but this technique suffers from poor detail in deep shadows and fails to depict linear features aligned with the light source. The study proposes using the sky‑view factor as a diffuse‑illumination relief visualization method to better display terrain characteristics. The method computes the sky‑view factor, representing the fraction of sky visible from each DEM cell, and uses it to generate a diffuse illumination map. Applied to high‑resolution archaeological DEMs, the sky‑view factor visualization enhances detection of small‑scale features.

Abstract

Remote sensing has become the most important data source for the digital elevation model (DEM) generation. DEM analyses can be applied in various fields and many of them require appropriate DEM visualization support. Analytical hill-shading is the most frequently used relief visualization technique. Although widely accepted, this method has two major drawbacks: identifying details in deep shades and inability to properly represent linear features lying parallel to the light beam. Several authors have tried to overcome these limitations by changing the position of the light source or by filtering. This paper proposes a new relief visualization technique based on diffuse, rather than direct, illumination. It utilizes the sky-view factor—a parameter corresponding to the portion of visible sky limited by relief. Sky-view factor can be used as a general relief visualization technique to show relief characteristics. In particular, we show that this visualization is a very useful tool in archaeology as it improves the recognition of small scale features from high resolution DEMs.