Two other key sources of data are geodesic (any changes to the curve of the Earth's surface) and the chemical composition of fluids and gases emitted from vents. Lin's team have installed more than 10 GPS stations near the most likely eruption sites at Dayoukeng, Xiaoyoukeng and Huangzuishan (the most seismically active locations) and apparatus at hot springs and fumaroles to constantly measure the concentrations and densities of marker compounds and isotopes, such as carbon dioxide and helium.
