of Mont Blanc is a thick, perennial ice-and-snow dome whose thickness varies. Therefore, no exact and permanent summit elevation can be determined, though accurate measurements have been made on specific dates. Its official elevation was for a long time. In 2002, the IGN and expert surveyors, with the aid of GPS technology, measured it to be . After the 2003 heatwave in Europe, a team of scientists remeasured the height on 6 and 7 September. The team was made up of the glaciologist Luc Moreau, two surveyors from the GPS Company, three people from the IGN, seven expert surveyors, four mountain guides from Chamonix and Saint-Gervais and four students from various institutes in France. This team noted that the elevation was , and the peak had shifted to a point away from where it had been in 2002. After these results were published, more than 500 points were measured to assess the effects of climate change and the mountain's height fluctuations at different points. Since then, the mountain's elevation has been measured every two years. The summit was measured again in 2005, and the results were published on 16 December 2005. The height was found to be , more than the previously recorded height. The rock summit was found to be at , some west of the ice-covered summit. In 2007, the summit was measured at and in 2009 at . In 2013, the summit was measured at and in 2015 at . From the summit of Mont Blanc on a clear day, the Jura, the Vosges, the Black Forest, and the Massif Central mountain ranges can be seen, as well as the principal summits of the Alps. Climbing routes Several classic climbing routes lead to the summit of Mont Blanc: The most popular route is the Goûter Route, also known as the Voie Des Cristalliers or the Voie Royale. Starting from Saint-Gervais-les-Bains, the Tramway du Mont-Blanc (TMB) is taken to get to the Gare du Nid d'Aigle. The ascent begins in the direction of the Refuge de Tête Rousse, crossing the Grand Couloir or Goûter Corridor, considered dangerous because of frequent rockfalls, leading to the Goûter Hut for night shelter. The next day the route leads to the Dôme du Goûter, past the emergency Vallot cabin and l'Arête des Bosses. La Voie des 3 Monts is also known as La Traversée. Starting from Chamonix, the Téléphérique de l'Aiguille du