Gerd Weitkamp Arnold Bregt Ron van Lammeren Agnes van den Berg Three Sampling Methods for Visibility Measures of Landscape Perception. 268-284 2007 conf/cosit/2007 COSIT http://dx.doi.org/10.1007/978-3-540-74788-8_17 db/conf/cosit/cosit2007.html#WeitkampBLB07