A tachometer is used to conduct this process. Contour lines for only chosen points are jotted down, and levels of the same lines are marked. Note down the direction of every contour line. Radial line method for points: This method requires one to note down various radial lines from a particular point in the selected area.This method works best when charting down contour lines for narrow roads, railway tracks, and canals. The spacing distance in this method ranges from 20 m to 100 m. Reduced levels of these points and found contour lines are also marked. Then these established points are jotted down in the drawing papers. Then using levelling, the lessened level of all the points is noted down. Cross-section method of selecting points: At regular distances, cross-section points are noted down at this method.Then levelling is done to note down all the grid points. All the squares must be of the same dimension. The size of the squares can be anywhere from 5 m to 30 m. Square method of selecting points: In this method, the points are read by dividing the area into small squares, and then the grid points are marked down.One can further use three different methods to find the correct reading point: This method is best suited for areas that have hills and depressions.
This process can also be called spot-level contouring. After surveying, their locations are plotted on the contour plan, and then drawn down using interpolation. Along with the contour lines, all the visible slopes, ridges, and depressions along the area are also surveyed. The reading is conducted on the spot levels of a group of contour lines laid all over the selected area. Unlike the direct method, the staff survey reading is not done on the contour lines. Indirect method of conducting a contour survey One must only use this method when the plotting area is smaller in size. This method does take up a lot of time before it is completed, but the results are always accurate. This way they note down many contour lines with points on them.įor the direct method, the plane table survey is best suited, which is a faster method of noting down the field monitoring and plotting together. Then again, the staff reading man is made to find another point with the same readings, and they repeat this process. The surveyor then sets the horizontal elevated control of the surveyed point by using his set of instruments. The person handling the staff reading instrument is then made to move to and fro in the area until accurate readings are noted down. Then the necessary staff reading for the selected contour line is calculated. Once a top fly shot of the selected area is conducted from a place nearer to the selected benchmark, a level can be set on the required position. One must use a vertical levelling instrument to conduct the survey in a direct method. This method requires one to pinpoint all the perpendicular and straight controls of the main points that lay on the chosen contour lines. There are mainly two methods a builder must follow to conduct a proper contour survey: Direct method of conducting a contour survey The instrument named ‘Clinometer’ is used to study the contour gradient.Ĭontour: Methods used to conduct contour survey Contour gradient– It is defined as a line that holds a constant disposition to the horizontal elevation.
There could be a difference in distances between contours as they depend on the alternate height and steepness between any slopes and elevations on the land.
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