"Visibility Analysis of Settings of Historic Places" was devised to assess the impact on the settings of listed buildings, scheduled monuments, conservation areas and historic parks and gardens in 2016 by Dr Peter Wardle. This followed the Environment Agency publishing their LIDAR data for the UK.
The Historic England 2015 document "The Setting of Heritage Assets" "advises the applicant to consider approaches such as a 'Zone of Visual Influence' (ZVI) or 'Zone of Theoretical Visibility' (ZTV) in relation to the proposed development in order to better identify heritage assets and settings that may be affected. A 'Zone of Visual Influence' defines the areas from which a development may potentially be totally or partially visible by reference to surrounding topography. The analysis does not take into account any landscape artefacts such as trees, woodland, or buildings, and for this reason is increasingly referred to as a 'Zone of Theoretical Visibility'."
The real world is very different with many "landscape artefacts" being present. In a development which is hidden from a Heritage Asset by topography clearly there is no impact on the visual setting. The reverse is also true, something located on a hilltop such as a hillfort will be seen many miles away so does this mean there is an adverse effect by building anything from which particular monument can be seen?
What is advocated here is a real world approach with real world features such as buildings and trees being taken into account as well as topography. In simple terms the way it works is this:
A digital terrain model, a matrix of height data, is analysed to see if there is a direct line of sight so that point X can be seen at point Y, or if some features prevent this.
In essence the basis of this analysis is that the computer can be used to determine if any two points are inter-visible, or if the view is blocked by a terrain or other feature. Prior to 2016 its use in Land Use planning was restricted to modelling road junctions and considering the impact of hard rock quarries.
This can thus determine what will be seen of a proposed building in an objective way. This therefore is the starting point for determining what the impact on the setting of a heritage asset is.
The advantages are:
1. Access to land or a building is not necessary.
2. Very large areas can be considered i.e. the impact of a tall building on a city wide basis.
The application of this type of analysis is not without its practical difficulties - the presence of a bus, for example, can produce misleading results. However the biggest difficulty is that it takes about a month of 2 powerful workstation's time to undertake the analysis.
This analysis has now been presented at appeal on a number of occasions and the professional judgements based on it have been accepted.
Example can be found on the following pages: