Scope Of Survey Topographical survey Road survey Existing Features Contour Survey Services, Site Location Pan India, Mode Of Report DWG FILE GIF

What is contouring in surveying?contouring in surveying is the assessment of elevation of various points on the ground and fixing these points of same horizontal positions in the contour map. To exercise vertical control leveling work is executed and simultaneously to exercise horizontal control chain survey or compass survey or plane table survey is intended to be carried out. If the theodolite is used, Both horizontal and vertical controls can function as achieved from the same instrument. Derived from the instruments used one can classify the contouring in different groups found in levels are, This method taken at some selected points and their levels are reduced. Thus in this method horizontal control is established first and then the levels of those points found. After locating the points on the plan, Reduced levels are marked and contour lines are interpolated between the selected points. For selecting points any among the items listed methods can serve as method of squaresmethod of cross, Sectionradial line methodcommonly used size of square varies from 5 m 5 m to 20 m 20 m. Levels of all grid points are established by levelling. Then grid square is plotted on the drawing sheet. Reduced levels of grid points marked and contour lines are drawn by interpolation ref. Fig. 1 . Method of cross, Sectionin this method cross, Sectional points are taken at regular interval. By levelling the reduced level of all those points are established. The points are marked on the their reduced, Drawing sheets levels rl are marked and contour lines interpolated. Radial line method fig. 3 . In this method several radial lines are taken from a point in the area. The course of each line is noted. On these lines at selected distances points are marked and levels determined. This method is Perfectly tailored for hilly areas. In this survey theodolite with tacheometry facility is commonly used. Drawing contoursafter locating contour points smooth contour lines are drawn connecting corresponding points on a contour line. French curves may is crafted to suit drawing smooth lines. A surveyor should not lose the sight of the characteristic feature on the ground. Every fifth contour line is made thicker for easy readability. On every contour line its elevation is written. If the map size it is, Is large written when finisheds also. Contour maps and its usesa contour maps consists of contour lines which are imaginary lines connecting points of equal elevation. Such lines are drawn on the plan of an area after establishing reduced levels of several points in the area. The contour lines in an area are drawn keeping difference in elevation of between two consecutive lines constant. The contour, For example map in fig. 1 shows contours in an area with contour interval of 1 m. On contour lines the extent of lines is also written. Characteristics of contour mapsthe contours maps have the following characteristics contour lines must close, Not necessarily in the limits of the plan. Widely spaced contour indicates flat surface. Closely spaced contour indicates steep ground. Equally spaced contour indicates uniform slope. Irregular contours indicate uneven surface. Approximately concentric closed contours with decreasing values towards centre fig. 1 indicate a pond. Approximately concentric closed contours with increasing values towards centre indicate hills. Contour lines with u, Shape with convexity towards lower ground indicate ridge fig. 2 uses of contour mapscontour maps are extremely useful for various engineering.