Contour plans are a
graphical representation of the lay of the land. They show the degree of slope
on a site. After contour survey plan architect can design a building plan with floor level.
The contour survey should be carried out before starting any project work.
On a contour map, the layout of all the building of the project is plotted.
Plinth/parking levels of the buildings, road levels, considering all storm water aspect, drainage levels etc. are decided with respect to all the plot levels with the help of a contour map.
Insist that the Architect/Plumbing Consultant and all other consultants should write R.L.s of each structure.
Contour map is useful for the following:
- To know the overall topography of land or plot.
- To decide the parking/plinth levels of each building.
- To decide all internal roads levels.
- To decide and design complete the drainage system for the entire project, considering natural slopes of the ground, invert levels of nearby nalla, drainage chamber etc. with minimum excavation and therefore, minimum cost.
- To reduce the cost of excavation and filling for roads/plinths etc. considering cutting, filling quantities at initial stages while planning and designing the building.
- To decide the levels of all development works such as garden/swimming pools, recreation facilities, septic tank, underground water tank etc.
Important points about levelling
-
Before bearing the work the instrument
level is setup and flying level are taken from the nearest permanent bench mark
near the survey site.
The level is then set in a commanding
position and accurately leveled. The height of instrument is determined by taking
a back site on the bench mark and adding it to the reduce level of the bench
mark from known elevation of the contours and the height of instrument the
required staff reading to fire points on the various contour lines
contour points are obtained to the first place of a decimal by sub-tracing the
elevation of each of the contours from the height of instrument (H.I.).
The staff is held an estimated position
of a point. It is then moved up down the slope until the desired reading is
obtained.
The
point so determine is marked by whites or by fixing the ranging rod.
Several points are thus determine and
mark on each contour in the length of 100 m.
Only arc contour is located within the
desired.
Having fixed the contour within the
desired length the level is moved and setup in a new position. The new height
of instrument(H.I.) and the required staff reading are then calculated in a
similar manner and the process is repeated until the whole area is surveyed.
The position of the contour points are
located by suitable methods of surveying.
The point are plotted on the plan and
contour are drawn by joining the points by plotted curve line.
