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Refer to the topographic map - NSC Geography - Question 2 - 2021 - Paper 2

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Refer to the topographic map. Calculate the magnetic declination for 2021. Show ALL calculations. Marks will be awarded for calculations. Clearly indicate the direc... show full transcript

Worked Solution & Example Answer:Refer to the topographic map - NSC Geography - Question 2 - 2021 - Paper 2

Step 1

Calculate the magnetic declination for 2021

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Answer

  1. Difference in years: To find the difference in years from 2014 to 2021, we calculate: 2021 - 2014 = 7 years.

  2. Mean annual change: According to the information provided, the mean annual change is given as 6°.

  3. Total annual change: The total annual change over the 7 years is calculated as: 7 years * 6° = 42°.

  4. Mean magnetic declination for 2021: The mean declination for 2021 can be calculated by adding the total annual change to the last recorded declination. If we assume the last recorded declination was 25°28', then:

    extMeanmagneticdeclinationfor2021=25°28′+42′=26°10′extwestoftruenorth ext{Mean magnetic declination for 2021} = 25°28' + 42' = 26°10' ext{ west of true north}

Step 2

Calculate the average gradient from station 31 (O) to benchmark 36.4 (P)

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Answer

  1. Vertical interval (VI): The height difference (vertical interval) between stations O and P is calculated as: 481.2 m - 36.4 m = 444.8 m.

  2. Horizontal equivalent (HE): The horizontal distance is given as 500 m.

  3. Average gradient: Using the formula: ext{Average gradient} = rac{VI}{HE} = rac{444.8}{500} = 0.8896 This provides a gradient of approximately 1:2.81, meaning for every 2.81 units horizontally, there is a 1 unit vertical increase.

Step 3

Why did the gradient limit the construction of a road?

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The gradient calculated (1:2.81) indicates that the slope is quite steep. Such a gradient would limit road construction because it poses challenges for vehicles to ascend or descend safely. Steep gradients can lead to concerns regarding vehicle stability and control.

Step 4

How did engineers construct the R43 to overcome the challenges?

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Engineers typically tackle steep gradients by designating routes along gentler slopes. They may also employ techniques such as:

  • Following the shape of the terrain to reduce elevation changes.
  • Routing the pathway around the steeper parts.
  • Utilizing switchbacks to create less aggressive gradients.

Step 5

Indicate the height of U on the vertical scale

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Answer

To indicate height U, one must refer to the provided vertical scale on the cross-section. If 1 cm represents 20 m, then measuring the height according to the contour lines will provide the height of U.

Step 6

Complete the cross-section using contour heights

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Answer

For the cross-section completion, use the contour heights indicated on the horizontal scale corresponding to the heights from points 6 to 7, ensuring the shape depicted on the cross-section accurately represents the elevations.

Step 7

Identify man-made feature V on the cross-section

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Answer

Man-made feature V can be identified as a structure or element depicted on the cross-section. This could include structures like a dam, bridge, or road, depending on the context provided in the diagram.

Step 8

Calculate the vertical exaggeration

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Answer

Vertical exaggeration is calculated using: ext{Vertical exaggeration} = rac{VS}{HS}

  • Where vertical scale (VS) is 1 cm for 20 m (or 1:2000) and horizontal scale (HS) is 1:10000. Therefore: ext{VE} = rac{1:2000}{1:10000} = 5 The unit of measurement is a ratio, indicating a 5x exaggeration in height compared to horizontal distance.

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