Isopleths

http://sarahpopesblog.blogspot.com/2011/04/isopleths.html

Isopleths use contour lines that have to be calculated using many different data points over a certain geographic area because it cannot be determined by one single data set. The map I chose shows the velocity of coastal wind of the coast of Columbia River by time and latitude. From the map it can be deduced that positive velocity occurs during the fall/winter seasons and negative velocity occurs during spring/summer seasons.