<Li> Topographic survey: a survey that measures the elevation of points on a particular piece of land, and presents them as contour lines on a plot . </Li> <P> Based on the considerations and true shape of the earth, surveying is broadly classified into two types . </P> <P> Plane surveying assumes the earth is flat . Curvature and spheroidal shape of the earth is neglected . In this type of surveying all triangles formed by joining survey lines are considered as plane triangles . It is employed for small survey works where errors due to the earth's shape are too small to matter . </P> <P> In geodetic surveying the curvature of the earth is taken into account while calculating reduced levels, angles, bearings and distances . This type of surveying is usually employed for large survey works . Survey works up to 100 square miles (260 square kilometers) are treated as plane and beyond that are treated as geodetic . In geodetic surveying necessary corrections are applied to reduced levels, bearings and other observations . </P>

Which survey assume the surface of earth as plane