ZVI

A visibility calculation can distinguish between partly and full visibility by selecting the top of the turbine as hub height as or blade tip height. The horizontal and vertical subtended angle can also be calculated to give a better understanding of the visual impact of the wind farm projects. The vertical subtended angle shows how large the wind turbines would appear in the landscape. The horizontal subtended angle documents the extent to which a wind farm will occupy the field of view. The visual impact of different layouts can easily be compared and documented with the result layer comparison option.

Radar ZVI also included

The Radar ZVI calculates whether given WTGs are visible from one or more radars and gives the corresponding clearance height. The radar ZVI planning map shows the areas where a WTG with specific dimensions could be installed while not being in the line of sight of radar(s).

Calculation Model

The calculation is made from a digital height model generated from digital height contour lines or a grid. Obstacles and areas with a height (e.g. forests, hedges, villages etc.) are also included. In principle, each calculation point sends a beam towards each WTG. Afterwards ZVI checks if the ray hits a hill, an area (with a defined height) or an obstacle and counts how many beams have reached their destination WTG. The calculation model takes into account the curvature of the earth (corrected in the case of radar calculation by the refraction constant).

Necessary Input Data (objects)

Please note, that the necessary objects (WTGs, Radars, Areas, Line/Grid Objects) are entered in the windPRO module BASIS.

Wind Turbine (position and type):

One or more WTGs are entered. Normally, the WTGs can be found in the WTG Catalogue, which contains more than 1,000 different types and models. WTG height and rotor diameter are included in the calculation. Wind farms are defined on different layers.

Height data Line Object (height contour lines):

Height data can be defined as lines or grid points. Data can be loaded from a file or downloaded from windPRO On-line data (e.g. SRTM data windPRO can read formats like dxf xyz, shp, hgt, grd, map, asc and ntf files.) Height contour lines can also be digitized directly on-screen.

Area Object (area with a height):

Areas can be digitized directly on-screen or a file with areas can be imported (e.g. .shp files). Each area type is given a height, e.g. forest with low or high trees, urban areas etc. You can define an arbitrary number of area types and give them individual heights.

Obstacles:

Obstacles (which can also be used in WAsP calculations) are boxes created on the map for buildings or hedges.

Radar:

One or more radars can be entered. They are defined by their effective height above the ground level which is the height of the radiation centre.

Calculation Report

The calculation report gives the following printout pages:

Summary: with the most important assumptions such as map section and WTGs included in the calculation. A pie diagram and tables show the distribution of areas with different numbers of visible WTGs or with the cumulative impact of wind farms. Similar results are provided for the horizontal subtended angle map, vertical subtended angle map and the radar planning map. With Radar ZVI, the clearance height between the tip height of the turbines and each radar beam is presented in a table.
Map: a map with raster presentation of visible WTGs or of the subtended angle. For a Radar ZVI the clearance height is shown on the planning map. The categories of visible WTGs, subtended angle values or clearance height can be given a separate color or a color scale arranged by number.