@incollection{TUW-256803, author = {Fogliaroni, Paolo}, title = {Visibility Relations}, booktitle = {Encyclopedia of GIS - Second Edition}, year = {2016}, editor = {Shekhar, Shashi and Xiong, Hui}, pages = {1--8}, publisher = {Springer Verlag}, keywords = {Visibility, 3D}, note = {invited} }