LoS Tools

QGIS plugin to create and analyse lines-of-sight. Provides also set of supporting tools. The plugin is focused on point to point visibility, in contrast to classic viewshed analysis which is point to area. Besides that it provides tools for identification of horizon points (on LoS), horizon lines (from a set of LoS) and also additional useful tools related to visibility analysis.

Plugin is available here: https://plugins.qgis.org/plugins/los_tools/

Important terms

Line-of-sight (LoS)

Line from a specific observer point (observer) that to or through specific target point. This plugin defines three types of LoS: local, global, without target.

The local and global LoS are used to describe visibility of specific target (i.e. highest point of building, top of the hill etc.) from observing points. Local LoS is strictly between observer and target and does not allow to assess the visibility behind the target. Global LoS is from observer through target but continues behind it as much as underlying elevation raster allows. Global LoS allows assesment of visibility of target with respect to surface located behind it.

LoS without target is a special case of LoS where the target point serves only as descriptor of direction and is not used to evaluate visibility at all. The target points for this can be generated by tools Create points around and Create points in direction. Sets of LoS generated using these tools can be used to identify horizon lines.

Horizons

Generally, horizon is a point on LoS that is visible and is immediately followed by an invisible point. There are several types of horizons mentioned in the plugin's tools. Mainly local and global horizons and horizon lines.

Global horizon is a horizon that is highest on LoS and if the surface raster extent is sufficient it should be the point where LoS meets the sky. LoS have just one global horizon.

Local horizon is any horizon on LoS that is not global. There may be any number of local horizons on LoS. Amogst these local horizons the highest local horizon can be useful for some analyses. The maximal local horizon is the highest horizon that is not global.

Citation

The citation for the plugin should be:

Jan Caha (2020). LoS Tools. QGIS Plugin version 0.2. https://jancaha.github.io/qgis_los_tools/
@Manual{,
  title = {LoS Tools},
  author = {Jan Caha},
  year = {2020},
  note = {QGIS Plugin version 0.2},
  url = {https://jancaha.github.io/qgis_los_tools/}
}