This solar model is a tool to predict the movement of shadows and check whether this prediction comes true. It helps to understand that the path of the sun changes with the seasons and that the design of buildings must take this into account.
For architects and engineers, it is indeed very important to take into account the evolution of sunlight in order to make the most of solar energy in houses (passive solar for daylight and heat) and for solar installations (photovoltaic cells and thermal collectors). This makes it possible, for example, to size solar protection (eaves or blinds) to protect against the sun in summer, while taking advantage of its contribution in winter.
These specialists use calculation tools such as the solar diagram. This diagram represents the view of the sun that an observer would have at a given point if he were to hold the diagram in front of his eyes and look south (see pp. 6-7). The 'masks', i.e. the elements of the landscape that obstruct the sun by casting a shadow, are then plotted on the diagram. By knowing in advance the location of the sun at any time of the year, it is possible to position buildings and solar installations accurately.