The Ossau Valley is one of 3 valleys in the Bearn Pyrenees. As part of the study of dark ecological network for the Pyrenees National Park, DarkSkyLab has carried out simulations using detailed street lighting data. An example of the results of these simulations is shown in the video below, in which we fly over the Ossau valley.

A sky quality map, the result of a simulation with Otus software, is applied to the Google Earth 3D map using the color levels defined on the Modeling page of this site. Light sources are shown for certain communes, and the color of the sources depends on their power (green if less than 100W, yellow if less than 200W, orange if less than 300W and red above).

The video also shows the effect that switching off a commune has on its environment: when the street lighting in the village of Aste-Béon is switched off, the entrance to the valley to the east of the village immediately becomes darker, with a clear change in color on the Bortle scale. It can also be seen that a 50% reduction in lighting power at the Gourette ski resort significantly reduces the impact in terms of light pollution over significant distances. Another aspect of the simulation presented concerns the increase in light pollution due to the reflection of public lighting on the snow (the impact has been estimated for the Gourette ski resort).

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