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Calculation of slope angles

Calculation of slope angles. The 2008 Level 3 S pecification for Skills says: Candidates will be required to calculate slope angle from a topographic map and provide an answer in degrees and percent. Slope angles can be expressed as:. An angle in degrees ° A percentage %.

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Calculation of slope angles

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  1. Calculation of slope angles The 2008 Level 3 Specification for Skills says: Candidates will be required to calculate slope angle from a topographic map and provide an answer in degrees and percent.

  2. Slope angles can be expressed as: An angle in degrees ° A percentage % • Learning how to calculate slope angle (gradient) as a degree and as a percentage before going into the 2008 exam would be wise.........also make sure you have a scientific calculator.

  3. Slope angles as degrees Two pieces of information are needed to work out degrees: The HORIZONTAL DISTANCE between two points on a map (expressed in metres) The DIFFERENCE IN HEIGHT between the lowest point and the highest point (expressed in metres) Note: • The horizontal distance and height need to be expressed in the same • unit of measurement • The slope angle will be an average over the distance, it will not take into • consideration valleys or peaks across that distance • Working out slope in degrees is simple by following five easy steps

  4. Step 2: Calculate the difference in height between the two points Step 3: Calculate the distance between the two points Step 1: Find the two points to calculate slope between 100m 200m 300m 325m B 325m – 100m = 225m 250m A to B is 3cm on the map. This is 1.5km but must be converted to same unit of measurement as height so it becomes 1500m 150m A Scale: 1:50 000 (1cm = 500m)

  5. Step 4: Apply the formula Slope = • difference in height (m) • horizontal distance (m) • 225m • 1500m • = 0.15 (gives a decimal answer) • Slope = Step 5: Work out the inverse tangent (by pushing shift Tan ¯¹ on your scientific calculator) to get the degrees • = 0.15 • =Tan¯¹ 0.15 • = 8.5° (1dp) • 8.5° degrees is the angle of slope

  6. Slope angles as a percentage Simply go back to the decimal answer (step 4) and convert to a percentage... o.15 x 100 = 15% The slope angle as a percentage is 15% So that is a gradient of 8.5° as a degree or a gradient of 15% as a percentage

  7. Acknowledgements • http://www.nzgs.co.nz/Resources.aspx#map accessed 9/6/08 • H. McMillan - Saint Kentigern College • Martin Newton • Nick Page - Otumoetai College

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