### How it works

TownScope is an urban open spaces analysing tool. To perform any analysis you need three components :
1- the scene model,
2- the analysis medium or element and,
3- the analysis processor.

Models can be generated in any CAD software. Main CAD file formats supported in this version of TownScope

Very important : the north direction is crucial for solar access calculations. TownScope considers this direction to be bottom-up on the screen when a scene is displayed in plan projection. You can change the orientation of your model in the CAD tool or through the transformation window.

Three types of analysis elements can be defined in TownScope :

- Points : list of distincts 3D points.
- Polyline : list of connected 3D segments and a step to divide each segment into a series of points. The analysis processor is executed on all the points generated by this division. The polyline points do not have to be in the same plan.

  Polyline element :

- Zone : list of 3D points representing a planar area. The points processed during an analysis are the nodes of a grid generated over the area's bounding box using a user-defined step. Only points on the border or inside the area are calculated.

  Zone element, calculated points in blue :

- You can also choose one or more surface in the 3D model and define it as an analysis zone.
  Since version 3.1.0 you can create multi-zone-element by selecting many surfaces in the model. (see short cut actions in the Main view pane section).

The analysis processors available in the current version are :

- Solar Access : This analysis calculates the direct radiation energy, the sky diffused energy (vertical sky component), the reflected energy from the surrounding surfaces and the sunshine duration. These calculations can be done for any day of the year and at any geographical location.
  An orientation vector is used in every solar access computation. The orientation vector and the 3D point where the calculation is performed define a plan representing an infinite opaque surface stopping any direct radiation coming from behind this plan.
  For each day, the calculation of nominal values for direct and diffused radiations uses geographical data (latitude, altitude) and weather data such as the atmosphere humidity, the site turbidity (air pollution),...
  The software uses spherical projections to compute the scene masks obstructing the direct and diffused radiations. The values of those masks depends on the properties attributed to the surfaces in the analysed scene (see Surfaces properties)
- Comfort evaluation : This analysis provides four values describing the human thermal comfort in an urban open space : Sweat rate, Sweat evaporation rate, Skin wetness and Sensation temperature.
  The calculation of these values uses the solar access processor to compute the received energies on six surfaces representing the human body (). Long-wave radiation is also computed in an approximate way. This last energy value depends on a number of parameters that are particularly difficult to estimate (surface temperature,...).
- Sky opening : This analysis uses the isoaire spherical projection (bottom-up) to evaluate the ratio of the visible sky area to the total area of the reference half sphere centred at the view point (observer).
- View lengths : This analysis uses the isoaire spherical projection (bottom-up) to compute five values :
  - Minimum view length : This is the minimum value of the distances between the observer and the surfaces in the scene.
  - Maximum view length : This is the maximum value of the distances between the observer and the surfaces in the scene.
  - Average view length (Lm): This is the mean value of distances (Li) between the view point (observer) and the visible surfaces weighted by the area (Si) of these surfaces after projection on the sphere. Lm = Sumi=1,n (SixLi) / Sumi=1,n (Si).
  - Characteristic view length : This is the ratio of the average view length to the area to which it refers : percentage of sky area obstructed. Lc = Lm / (Sumi=1,n (Si) / Stotal)
- Visibility : Using isoaire spherical projection, this analysis computes on each point the visible portion of the user's selected surfaces in the scene. The result values are :
  - Relative rate [%] : ratio of area of visible portions of the selected surfaces to their total area.
  - Absolute rate [%] : ratio of area of visible portions of the selected surfaces to total area of all visible surfaces.

In general, to perform any analysis :

- Load the scene file (main window tool bar).
- Define the analysis element(s) you want to use.
- Select the analysis processor, create your calculation object and execute it over the defined element.
- Finally, you can display the result values in the main view pane according to the choices you select in the results viewing window.

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