Abstract: Two dimensional convex hull is one of the typical problems in computational geometry and widely applied in GIS.In convex hull,some points in the convex hull,such as the points lie in the line between the two convex points but not convex points.How to seek the convex points is the key issue of the convex hull algorithm.An improved algorithm of two dimensional convex hull based on included angle is proposed,and all the convex points are achieved through the maximal included angle by the increasing counter-clo...