The altitude of the Kathmandu Valley has elevated by 80 cm following the April 25 earthquake, authorities said on Thursday."The altitude of the valley increased by 80 cm as the Indian tectonic plate moved further to the Tibetan plate during the quake," said Madhu Sudan Adhikari, director general of the department of survey, Xinhua news agency reported.According to a Global Positioning System (GPS) survey carried out by the department, the altitude of the valley has risen slightly.The Kathmandu Valley is now situated at an altitude higher than what was 1,338 metres above the sea level before the 7.9-magnitude quake.The 24-hour GPS survey was conducted from five control stations on hills surrounding the valley four days after the devastating quake.