Depth below horizon: new (old) functionality for QGIS viewshed analysis

The basic idea of visibility analysis is to test whether particular locations are theoretically observable from a given observer point (« theoretically » because our data and algorithms can never ideally replicate real-world situations). Such a query yields a yes/no answer for each tested point, which is typically represented as Boolean raster in GIS software. … Continue reading Depth below horizon: new (old) functionality for QGIS viewshed analysis

Visibility analysis for QGIS 3.0 : tackling big data

Viewshed plugin for QGIS is based on Numpy library for handling raster data. Numpy is tuned for high performance and is (relatively) easy to use. However, it relies heavily on available live memory and will break with voluminous datasets. Which is what elevation models usually are... Version 0.6.4 introduces an addition to the original algorithm … Continue reading Visibility analysis for QGIS 3.0 : tackling big data

Land visibility in the Mediterranean: a large scale model

Visibility of land was a major consideration for ancient seafaring, for reasons of navigation and security. Even if the open sea travel must have been practised already by the Neolithic period, judging by the colonisation of remote islands and by the exchange of artefacts across the Mediterranean, the sight of the land remained a much … Continue reading Land visibility in the Mediterranean: a large scale model

Benchmarking viewshed algorithm: Nuraghi of Sardinia

The new viewshed plugin for QGIS 3 features an improved algorithm which should result in perceptible improvements in terms of efficiency. So let's give it a try! Nuraghe in Toralba-Sant'Antine © Michel Royon / Wikimedia Commons The test data I'm using are the famous nuraghi of Sardinia, drystone towers dating to the 2. millennium BC. … Continue reading Benchmarking viewshed algorithm: Nuraghi of Sardinia

Visibility analysis for QGIS 3.0

Visibility analysis plugin is now available in QGIS 3.0! It has been completely refurbished: from now on it will be integrated into the "Processing toolbox". This is a more appropriate habitat for the algorithm because of integration with the QGIS toolshed. It can be now combined with all the fancy geoprocessing tools (GRASS, SAGA etc). … Continue reading Visibility analysis for QGIS 3.0