Isoline maps

Isoline maps are a type of thematic maps that uses lines to connect the like numbers in a map, very similar to topo maps. In this map above it is showing the annual precipitation in Washington in 1996. The higher precipitation is shown with the darker shade of purple. http://www.google.com/imgres?imgurl=http://lostmanmaps.com/gallery/wash-precip.gif&imgrefurl=http://lostmanmaps.com/gallery.html&usg=__jD229S4Yg2E0W8RR_zo9Js5WK9s=&h=525&w=700&sz=20&hl=en&start=0&zoom=1&tbnid=mkuZUfXtss5FOM:&tbnh=123&tbnw=202&ei=W0UiTue2IImCtgfXx7SkAw&prev=/search%3Fq%3DIsoline%2Bmaps%26um%3D1%26hl%3Den%26sa%3DN%26biw%3D1363%26bih%3D740%26tbm%3Disch&um=1&itbs=1&iact=hc&vpx=529&vpy=262&dur=4376&hovh=194&hovw=259&tx=119&ty=133&page=1&ndsp=27&ved=1t:429,r:9,s:0&biw=1363&bih=740