Plane surveying is the survey in which the earth surface is assumed to be a plane and the curvature of the earth is ignored. The plane surveys extend only over small areas and the lines connecting any two points on the surface of the earth are treated as straight lines and the angles between such lines are taken as plane angles.
Moreover
In
plane surveying, the area under consideration is taken to be a horizontal plane
and the measurements plotted will represent the projection on the horizontal
plane of actual field measurements. A horizontal plane is one which is normal
to the direction of gravity as defined by “Plumb Bob”
at a point, but due to the earth, the plane will be tangent to the surface of
the earth at that point.
For
long enough area, there will be a difference between the area of horizontal
plane & the area on the curved surface of the earth.
It
can be shown that for surveys up to 100 sq. miles in area,
this difference is not serious. Therefore plane surveying will be adequate for
all but very largest survey.
American
surveyors put the limit at 250 km2 for
treating the survey as a plane.
Scope and Use of Plane Surveying
Plane surveys are carried out for engineering projects on a sufficiently large scale to determine relative positions of individual features of the earth surface. Plane surveys are used for the layout of highways, railways, canals, fixing boundary pillars, construction of bridges, factories etc. The scope and use of plane surveys are very wide. For the majority of the engineering project, plane surveying is the first step to execute them. Plane surveys are basically needed for proper, economical and accurate planning of all engineering projects and their practical significance cannot be overestimated.
Division of Plane Surveying
Plane surveying can be divided in the following ways.
- Chain Surveying
- Traverse Surveying (compass and theodolite surveying)
- Plane Table Surveying
- Ordinary Leveling
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