Question

Which of the following will be most suitable two standard parallels when the area to be represented extends from 20^°S to 80^°S?

• A. $30^{\circ}S$ and $70^{\circ}S$
• B. $20^{\circ}S$ and $40^{\circ}S$
• C. $80^{\circ}S$ and $40^{\circ}S$
• D. $40^{\circ}S$ and $50^{\circ}S$

Hint:

For two standard parallels, divide the range into six parts and place the parallels one-sixth away from the top and bottom boundaries.

Answer 1

The Correct Option is A

Concept: In Conical Projections with two standard parallels, the accuracy of the map is highest at these parallels[cite: 263]. To minimize overall distortion, the standard parallels should be chosen at specific intervals within the latitudinal extent of the map[cite: 279].

Step 1: Calculating the Latitudinal Extent.
The area spans from $20^{\circ}S$ to $80^{\circ}S$[cite: 263, 279]. The total latitudinal range is: $80^{\circ} - 20^{\circ} = 60^{\circ}$[cite: 263, 279].

Step 2: Applying the One-Sixth Rule.
A common cartographic rule for selecting standard parallels is to place them at one-sixth of the range from each edge[cite: 263, 279].
• Range = $60^{\circ}$.
• One-sixth of range = $60^{\circ} / 6 = 10^{\circ}$.

Step 3: Final Selection.

• First Parallel: $20^{\circ}S + 10^{\circ} = 30^{\circ}S$[cite: 264, 280].
• Second Parallel: $80^{\circ}S - 10^{\circ} = 70^{\circ}S$[cite: 264, 280]. This ensures the distortion is evenly balanced across the map[cite: 279].