The following are some of the uses of existing conditions contour lines.ġ) Determining the elevation of a given point on a plan.Ģ) Figuring out which direction on a plan is uphill and which direction is downhill.ĥ) Figuring out high points and low points on a plan. You would also see contour lines in as-built survey plans that are created after a new project has been constructed. Where You Would See Contour Lines Created From SurveyingĬontour lines created from surveying are shown in existing conditions plans in conjunction with other existing features of the survey area such as buildings, driveways, and roads.Ĭontour lines are also shown on proposed grading plans to show where proposed grading contours tie into the existing ground. If you were to walk along a piece of land along a line that is represented on a plan by a contour line for an elevation of 250 feet, the path you walk would be flat at an elevation of 250 without walking either uphill or downhill.Īn existing contour line that is surveyed is usually shown as a dashed line on a plan and is often times screened out (shown as a light gray) in order to not clutter the plan so that other features stand out better. It is shown as a line along a path of equal elevation. It represent by V –shaped.A contour line in land surveying is a two-dimensional representation of an elevation across an area of land that is drawn on a plan or map. Line joining the lowest point of a valley across the contours at right is called Valley line. ![]() If the higher values are outside the loop in the contour it indicates a Valley. Line joining the highest point of a hill across the contours at right angles is called Ridge line. If the higher values are inside the loop in the contour it indicates a Ridge. For a hill reading increasing towards center, and for a pond reading decreasing towards center. Close contour loops represent either a hill or pond.Irregular contours represent rough terrain.Ridge line / Valley line intersects contour at right angle.But if contours are distant then it shows a relatively mild slope. If the contours are closely spaced then it shows steep slope.A series of closed contour line on the map represent depression, if the higher values are outside.A series of closed contour line on the map represent a hill, if the higher values are inside.If contours are parallel and equally spaced then it represents a uniform slope.In this case, several contours coincide and the horizontal equivalent become zero. Contour lines never run into one another except in the case of a vertical cliff.Contour line do not merge or intersect each other except in the cases of an overhanging cliff or cave in the hillside.A contour line is a closed curve, however they may close either on the map itself or outside the map.All the points of a contour line have the same elevation.The contour interval depends upon several factors as.Smaller contour interval is more precise for the analysis.Generally contour intervals are taken 1 to 15m.It is desirable to have a constant contour interval, however in some special cases, a variable contour may also be provided.Elevation difference between two consecutive contours is called the contour interval.To calculate the amount of cutting, filling, and reservoir capacity. ![]()
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