The ArchaeoLines plugin displays any combination of declination arcs most relevant to archaeo- or ethnoastronomical studies.

ArcGIS toolbox for fuzzy viewshed calculation.

Calculates visible surface from a given observer point over a digital elevation model. The plugin is intended for more complex modelling, such as the depth below the visible horizon or generation of intervisibilty networks between groups of points. It is particularly performant for multiple viewshed calculations form a set of fixed points.

A toolbox for modelling human perception of topography for QGIS, based on QGIS viewshed module.