Tranquillity (also spelle tranquility or called equanimity) is the quality of calm experienced in places with mainly natural features and activities, free from disturbance from man-made ones. As such it is a public good and can be seen as an indicator of environmental quality. Although harder to measure than other indicators such as water or air quality, by analysing the various factors that contribute to tranquillity it is possible to produce maps which show the relative tranquillity of different areas.