7 Topographic Maps

Adapted by Joyce M. McBeth, Sean W. Lacey & Tim C. Prokopiuk (2018) University of Saskatchewan from Deline B, Harris R, & Tefend K. (2015) “Laboratory Manual for Introductory Geology”. First Edition. Chapter 3 “Topographic Maps” by Karen Tefend and Bradley Deline, CC BY-SA 4.0. View Source.

7.1 INTRODUCTION

A topographic map is a useful type of map that adds a third dimension (vertical) to an otherwise two-dimensional map defined by the north, south, east, and west compass directions. This third dimension on a topographic map is represented by contour lines, which are imaginary lines drawn on a map that represent a constant elevation above either average sea level (a.s.l.) or mean sea level (m.s.l.). A map with such elevation lines will provide the map reader with detailed information regarding topography (the shape of Earth’s surface). Knowledge of how to interpret a topographic map will allow a person to locate and identify features on Earth’s surface such as hills, valleys, depressions, steep cliffs and gentle slopes. In addition, the map reader will be able to identify areas that may be prone to geologic hazards such as landslides and flooding. Any person interested in purchasing property, landscaping, planning a hike or camping trip, or who needs to survey an area for construction of a road, dam or building, will want to first consult a topographic map.

7.1.1 Learning Outcomes

After completing this chapter, you should be able to:
• Recognize topographic patterns and geologic patterns
• Read and construct contour lines
• Determine gradients
• Read map scales and convert fractional scales
• Construct a topographic profile

7.1.2 Key Terms

• Bar Scale
• Benchmarks
• Contour interval
• Contour line
• Equator
• Fractional (ratio) scale
• Gradient
• Hachure marks
• Index contour
• Latitude
• Longitude
• Prime Meridian
• Relief
• Topographic profile
• Verbal scale
• Vertical exaggeration