Geographical analysis and numerical quantification of ...2012.ogrs-community.org/2012_papers/d2_6_minelli_presentation.pdf · Geographical analysis and numerical quantification of

Geographical analysis and Geographical analysis and numerical quantification numerical quantification

of visual impact for aerogenerators of visual impact for aerogenerators and photovoltaic panels and photovoltaic panels using Open Source GISusing Open Source GIS

A. Minelli, A. Minelli, I. Marchesini,I. Marchesini, P. De Rosa, L. Casagrande & M. Cenci P. De Rosa, L. Casagrande & M. Cenci

Gfosservices Gfosservices Studio AssociatoStudio Associato

Regione Regione UmbriaUmbria

Gfosservices Gfosservices

Studio AssociatoStudio AssociatoRegione Regione UmbriaUmbria

Sun and wind farm: the visual impactSun and wind farm: the visual impact

It seems the heaviest tomost of the people

Is it possible to quantify it?

To quantitatively define the visual impact we developed a GRASS GISGRASS GIS module:module:

Gfosservices Gfosservices Studio AssociatoStudio Associato

Regione Regione UmbriaUmbria

r.wind.sunr.wind.sun

Visibility quantificationVisibility quantification



Aerogenerators: InputAerogenerators: Input

Vector layer of aerogenerators positionHeigth of the aerogenerators

Computational distance

DEM



Photovoltaic panels: inputPhotovoltaic panels: input

Vertical dimension of the single panel

Maximum computational distance

Panel height above the ground

Horizontal dimension of the single panel

Inclination of panel

Azimuth of the panel

Minimum computational distance

Vector layer of panels position (centroid)

DEM



I = impact index (relative size of the object)Aobj = distorted object sizeAFOV = observers' Field Of View

The impact indexThe impact index

I=AobjAFOV



We define the static FOV as an ellipsoidal, three-axes, shapeThe dimensions of the FOV axes depends on: ● the distance “d” ( from the observer) at which FOV is calculated● three angles: - Nose = 85° - Superior = 65° - Inferior = 70°

i=d*tg(70°)

s=d*tg(65°)n=d*tg(85°)

Static Field Of ViewStatic Field Of View

d



First approach: from his point of view the observer can rotate his view all around 360°

Dynamic Field Of ViewDynamic Field Of View

Height: h= (s+i)Circumference: l=2πd



The dynamic FOV is the internal area of a cylinder: I*h.


h= (s

+i)

l=2πd

This approach is adopted to calculate the FOV for the assessment of the visual impact due to the photovoltaic panels



Second approach: from his point of view the observer can both rotate his view all around 360° and look up and down

The dynamic FOV area is the area of a sphere: A=4πd 2.


Since both horizontal and vertical dimension of the aerogenerators are not negligible, this approach is adopted to estimate FOV for the assessment of the aerogenerators visual impact



Perceived shape and sizePerceived shape and size

Fixing a projective plane Π , the relative size and shape (red line) depends on:

● the distance (d) between the object and the observer;● the mutual observer – object height (∆h).

d



Perceived shape and sizePerceived shape and sizeIn general, the projective plane Π can also be placed at a distance r != d.In that case the field of view is also estimated at the distance “r”. In that way the ratio between field of view and the object size is maintained constant

d

r



An aerogenerator has a quite complex shape.

In order to simplify the analysis, the area covered by the rotor is considered completely filled.

Aerogenerators: perceived shape and sizeAerogenerators: perceived shape and size



Two components are considered separately: tower and rotor

The size becomes the sum of the areas of a trapezius (tower) and an ellipse

In fact the rotor vertical axis is quite ever deformed from the point of view of the observer


tower

rotor



If the aerogenerator is fully visible:the center of view (red point) is placed between the rotor and the tower




The length of vertical axis of the ellipse and the heigth of the trapezium are calculated




Since the aerogenerator rotor can turn (to be ever perpendicular to the main wind direction), the width of the rotor ellipse is, conservatively, not altered





If the terrain hides a large part of the tower: the tower is not considered for the analysis



If the terrain covers up also part of the rotor:

only half of the rotor area is considered




Considering a single aerogenerator, it is possible (using a DEM) to evaluate the Impact Index map.For each point (raster cell) of the surrounding area:

Single Aerogenerator: Impact indexSingle Aerogenerator: Impact index

I=AobjAFOV



The Impact Index apply also in case of multiple aerogenerators

Multiple aerogenerators: Impact IndexMultiple aerogenerators: Impact Index

I=∑ AobjAFOV



Photovoltaic panels: perceived shape and sizePhotovoltaic panels: perceived shape and size

The problem of relative shape and size change also apply to the Photovoltaic Panels.

The size an shape change both vertically …...... and horizontally



Photovoltaic panels: perceived shape and sizePhotovoltaic panels: perceived shape and size

Fortunately the distorted shape of a rectangle is a parallelogram or a trapezium, so it is easy to calculate its the area.



The Impact Index must be calculated for each panel or group of panels.

Photovoltaic panels: Impact IndexPhotovoltaic panels: Impact Index

I=∑ AobjAFOV



r.wind.sun: resultsr.wind.sun: resultsThe r.wind.sun output is a raster layers of the sum of the impact index calculated for each photovoltaic panel or aerogenerator



r.wind.sun: resultsr.wind.sun: resultsGenerally speaking the value of each cell represents the occupancy, of the field of view, determined by the presence of all the aerogenerators or photovoltaic panels



The raster layers can be reclassified to be easily interpreted.

r.wind.sun: resultsr.wind.sun: results



The 3D visualization allows to highlight the effect of the partial hiddenness, due to the terrain, of the aerogenerators


23

43

2

2

3

4

5

6

1

Aerogenerators

1=low impact……6=high impact

The Impact Index values decrease towards the aerogenerators



Moreover, by means of the GRASS GIS nviz tool, the r.wind.sun module allows for a 3D view of the aerogenerators




● The module r.wind.sun is a preliminary answer to the question concerning the possibility to estimate the visual impact of aerogenerators and photovoltaic panels● We acknowledge that the relative dimension is only a part of the visual impact assessment● We put in evidence that this method can be used for other kinds of landscape offending structures ● We emphasize that, using a common field of view approach, the results obtained for different kind of structures, that exist on the same territory, can be combined.

r.wind.sun: conclusionsr.wind.sun: conclusions



r.wind.sun: downloadr.wind.sun: download

r.wind.sun is written in Python and will be soon available at the GRASS GIS addons web page:http://grass.osgeo.org/wiki/GRASS_AddOns

Thanks for the attention!Thanks for the attention!

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Geographical analysis and numerical quantification of ...2012.ogrs-community.org/2012_papers/d2_6_minelli_presentation.pdf · Geographical analysis and numerical quantification of