Isohyets

http://www.greenstone.org/greenstone3/nzdl%3Bjsessionid=BE6CA174E1D79367FF2F3BF5D3F2769D?a=d&c=ccgi&d=HASH01815a5264fa0f4bfa328693.9.np&sib=1&p.s=ClassifierBrowse&p.sa=&p.a=b

Isohyet maps are used to determine the amount of rainfall in a particular area.  Isohyet maps have lines with connecting points of equal rainfall in a given period.