In our case, we are not interested in what could be seen from sites B, but rather whether these sites could be seen from anywhere around and whether locations with good visual connections were preferred. It wouldn’t have much sense to switch these two – looking from ground level to a possibly non-existent target – which means we need to take care of target and observer heights. Now, there is a problem of mutual intervisibility: usually we test visibility from some arbitrary eye-height towards bare ground. each point on a map will show how many observers could see it. The result would be a cumulative visibility map, i.e. We need, then, to calculate all visibility areas from B sites and add them up. We can imagine two approaches to the problem: either we calculate visibility from A sites and test whether B sites tend to gather in their field of view or we calculate visibility areas from B sites and check whether A sites show a preference for good visibility zones. For instance, is visibility a factor in the choice of settlement location?įor the purpose of this exercise, we would like to know whether sites A betray a preference for areas providing good visibility to sites B.įirst step, obviously, we need to load the data in QGIS (any set of two shapefiles with points and one elevation model in raster format would do – provided coordinate reference systems match). ![]() The area in question is Istria (Croatia and Slovenia) and the projection is MGI Balkans 5 (EPSG : 31275).Ī most basic use for the visibility analysis would be exploratory: would someone be able to see point B from point A? Such a query can be made by any viewshed algorithm available - but what about many observers from a number of points? In fact, when studying ancient landscapes we are often interested not only of what people could see, but also whether visibility influenced their preference for particular locations. It comprises a DEM extracted from publicly available SRTM data (90 m resolution) and two sets of points (let’s call them A and B) which mostly correspond to archaeological sites I’m working on. The data which will be used can be downloaded from the plugin’s GitHub repo (link below). I’ve had a remark recently that some kind of tutorial would be welcome for the visibility plugin. For a tutorial made for QGIS 3, please go to. ![]() Important: This tutorial was made for QGIS 2, which is deprecated.
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