Lecture Notes: Creating Topographic Cross-Sections

Introduction

• Purpose: Understand how to create a cross-section from a topographic map.
• Example location: Perisher Valley near Little Thredboe River.

Steps to Create a Cross-Section

Step 1: Visualize the Terrain

• Use contour lines from the topographic map.
• Example: Cross-section from Pendley Gap to Bull Creek.

Step 2: Simplified Diagram

• Spot height given: 476 meters.
• Contour interval: 10 meters.
• Elevations: 476 (spot height), 470, 460, 450, 440, down to 430.
• Important to double-check elevations.

Step 3: Marking Contour Intersections

• Use a piece of paper to mark where contour lines intersect.
• Mark the elevations on the paper.

Step 4: Setting Up Graph Paper

• Draw X and Y axes.
• Scale of the map: 1:25,000.
  • 1 cm = 250 meters.
• Vertical scale must be exaggerated for clarity.

Vertical Exaggeration

• Purpose: Enhance the visibility of topographic features.
• Recommended vertical exaggeration: 5 times the horizontal scale.
• Calculation: Divide 25,000 by 5 for a scale of 1:5,000.
  • 1 cm = 50 meters.
• Ensure the vertical scale is larger to show topography better.

Step 5: Plotting the Cross-Section

• Mark the elevation at each tick mark on your cross-section.
• Use graph paper for accuracy.
• Plot points: 440, 450, 460, 470, etc.
• Draw lines to connect points and form the cross-section.

Challenges & Tips

• Importance of choosing the right vertical exaggeration.
• The vertical exaggeration affects the topographic clarity.
• Experiment with different scales to find best representation.

Conclusion

• Vertical exaggeration is crucial for effective topographic cross-sections.
• Adjust the exaggeration based on the topography (hilly vs. flatter areas).
• Practice with different scales to understand the impact on visualization.