plans and maps

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A plan is the graphical representation,to some scale , of the features on,near or below the surface of the earth as projected on a horizontal plane which is represented by plane of the paper on which the plan is drawn.However,since the surface of the earth is curved and the paper of the plan or map is plane,no part of the surface can be represented on such maps without distortion. In plane surveying,the area involved are small,the earth's surface may be regarded as plane and hence map is constructed by orthographic projection without measurable distortion. The representation is called a map if the scale is small while it is called a plan if the scale is large.On a plan ,generally,only horizontal distance and direction are shown. On a topographic map,however, the vertical distances are also represented by contour lines,hachures or other systems.