# Visibility Assessment of New Photovoltaic Power Plants in Areas with Special Landscape Value
## 1 Introduction
For assessing the aesthetic impact of PV plants, an indicator based on four parameters is proposed in [13], similar to the indicator presented in [10] for wind farms. In addition, in PV plants, there is a risk of glare from the reflection of sunlight on the surface of the PV modules, which makes them visible from great distances, producing a landscape alteration and negative visual impact on the environment [14]. Geographic information systems (GIS) are tools that make it possible to organize, analyse and model large amounts of spatial data, which facilitates the creation of maps for decision making in various types of projects. The scientific and technical literature includes many applications of GIS. Among other applications, they can be used to help in the assessment of renewable energy resources. For solar energy resources, [PERSON] et al. [15] assess the PV potential in southern Tyrol, northern Italy, taking into account PV facilities on roofs and non-conventional surfaces. In a GIS, it is possible to perform a spatial analysis of the solar resource data together with other data from the area under survey, such as orography and distances to roads and power lines, or even take climatic data into consideration, which can help to locate the best sites for building PV plants [16]. A GIS system is also a good tool for visual impact assessment: it is possible to generate maps of the region under study that show those areas where the installation of PV power plants would have less impact, or areas where the installation of these facilities would not be suitable due to their high visual impact on the environment. [PERSON] et al. [17] address visual impact from spatial and perceptual points of view. From the spatial point of view, the result is a visibility map in which each cell (geographic position) has a Boolean value indicating whether an installation built in that position is seen from the observer's location, and from the perceptual point of view, a visual perception map is obtained in which each cell is assigned the affected angle of vision. The parameters required by the model are the dimensions of the facility (height and width), the visual threshold (maximum distance from which a facility can be recognized), and the height of the observer's position. [PERSON] et al. [18] present a study that takes into account criteria of visibility and visual impact in the design stage of wind farms. The proposed methodology is based on two indices that describe the conditions of visual intrusion. The first index, called Magnitude of the Visual Effect (MVE), is the product of three visual indicators (visually affected area, visually affected population and visual exposure in linear sections), and the second one is an improved version of the Spanish Method index (SPM) proposed in [19]. Other authors take into account the visual capacity of the observer for visual impact assessment, using GIS tools to generate 3D maps [20]. For the assessment of the visual impact of wind turbines, other methods take into account the height of the visible part of the wind turbine and what percentage of it occupies the scene, for which GIS software together with 3D graphics generation software have been used [21]. Assessing the visual impact of PV plants using GIS-based tools helps to select geographic locations where the visual impact is lower. In [22], a relative visual impact index is defined, taking into account aspects such as the number of inhabitants in the surrounding area, the orography of the terrain and the height of the PV plants. From this index, visual impact maps are generated for two types of PV power facilities (with fixed panels or with trackers). Most of the GIS software have tools that make it possible to determine the visible geographic area (viewshed) from one or several observation points. Reference [23] proposes a methodology based on the fuzzy viewshed and the distance decay methods, which enables the calculation of the maximum number of hours in an average day in which a new PV plant can be seen by every possible observer.