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Review. Week 6 CVL 305A. 1. What is another name for the Grid Contour Method? Borrow pit Method 2. What determines the grid spacing when calculating volume using the grid contour method? size of site elevation changes accuracy required.

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Review

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  1. Review Week 6 CVL 305A

  2. 1. What is another name for the Grid Contour Method? • Borrow pit Method 2. What determines the grid spacing when calculating volume using the grid contour method? • size of site • elevation changes • accuracy required

  3. 3. How is the current elevation at a grid intersection point (i.e. corner of the grid) calculated, if no contour lines cross that point? • Scale distance (along grid line) between contour lines • Change in Elevation Per m = Difference in elevation ÷ Scaled Distance • Scale distance from contour line to grid corner • Elevation = Contour Elev + (Change in Elev)(Scale Distance)

  4. 4. How do you determine if you have a cut or fill in a grid? • difference between the average current elevation (for the grid) and the future site elevation 5. If a grid has both cut and fill, what short-cut can be taken when calculating the area of cut and the area of fill? • Use a simple shape to determine one of the areas • Remaining area = Grid Area – Area determined above

  5. 6. If the entire grid is a fill how do you calculate the volume of earth required? • Volume = Grid Area x Height of Fill

  6. Area by Planimeter • a planimeter is a mechanical instrument used to compute the area of a planar region • planar region • two dimensional surface • map • survey of a property • planimetersare used to calculate the area of two dimensional irregular shaped surfaces • alternate method would be to use geometric shapes

  7. Planimeter basic procedures • secure drawing to table • position instrument so that it can be moved to cover entire drawing during tracing procedure • turn instrument ON and follow directions as posted • record data • perform calculations

  8. Calculations • A = D x N2 • Area = A • Displayed number = D • Scale = 1:N • Example for metric: • scale = 1:100 • reading on the display is 250 cm2 • A = 250 cm2 x 100 x 100 = 2,500,000 cm2 = 250 m2 • 1 m2 = 10,000 cm2

  9. Calculations • Example for imperial: • scale = 1”=20’ • 20 x 12 = 1:240 • reading on the display is 150 in2 • A = 150 in2 x 240 x 240 = 8,640,000 in2 = 60,000 ft2 • 1 ft2 = 144 in2

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