# Terrain prickliness: theoretical grounds for low complexity viewsheds

## Abstract

An important task in terrain analysis is computing viewsheds. A viewshed is the union of all the parts of the terrain that are visible from a given viewpoint or set of viewpoints. The complexity of a viewshed can vary significantly depending on the terrain topography and the viewpoint position.

In this work we study a new topographic attribute, the prickliness, that measures the number of local maxima in a terrain from all possible perspectives. We show that the prickliness effectively captures the potential of terrains to have high complexity viewsheds. We present near-optimal algorithms to compute it for TIN terrains, and efficient approximate algorithms for DEMs. We validate the usefulness of the prickliness attribute with experiments in a large set of real terrains.

# Terrain prickliness: theoretical grounds for low complexity viewsheds

Proc. 11th International Conference on Geographic Information Science, 2021

To Appear.
@incollection{prickliness2021,
author = {Acharyya, Ankush and Jallu, Ramesh and  L{\"o}ffler, Maarten and
Meijer, Gert and Saumell, Maria and I. Silveira, Rodrigo and
Staals, Frank and Raj Tiwary, Hans},
title = {Terrain prickliness: theoretical grounds for low complexity viewsheds},
booktitle = {Proc. 11th International Conference on Geographic Information Science},
year = {2021},
location = {(online)},
series = {Leibniz International Proceedings in Informatics (LIPIcs)},
publisher = {Schloss Dagstuhl--Leibniz-Zentrum fuer Informatik},
numpages = {14},
category = {terrains},
note = {To Appear.},
}


# Terrain prickliness: theoretical grounds for low complexity viewsheds

Abstr. 37th European Workshop on Computational Geometry (EuroCG), 2021

@article{prickliness_eurocg,
author = {Acharyya, Ankush and Jallu, Ramesh and  L{\"o}ffler, Maarten and
Meijer, Gert and Saumell, Maria and I. Silveira, Rodrigo and
Staals, Frank and Raj Tiwary, Hans},
title = {Terrain prickliness: theoretical grounds for low complexity viewsheds},
journal = {Abstr. 37th European Workshop on Computational Geometry (EuroCG)},
year = {2021},
location = {St. Petersburg, Russia (online)},
numpages = {7},
category = {other},