1. Topographic Maps

2. Understanding Topographic Maps
Topographic maps are two-dimensional representations of a portion of the three-dimensional surface of the earth.
Topography is the shape of the land surface, and topographic maps exist to represent the land surface.

3. Understanding Topographic Maps
Topographic maps are tools used in geologic studies because they show the configuration of the earth’s surface.
Cartographers solve the problem of representing the three-dimensional land surface on a flat piece of paper by using contour lines, thus horizontal distances and vertical elevations can both be measured from a topographic map.

4. Topographic Quadrangles
Quadrangles are sections of the Earth that are bounded by lines of
latitude at the top (north) and bottom (south)
Longitude on the right (east) and left (west)

5. Topographic Quadrangles
Longitude and latitude are measured in degrees, minutes and seconds.
1 degree (o) = 60 minutes (‘)
1 minute = 60 seconds (“)

6. Compass Bearing A bearing is the direction from one point to another
If direction is expressed in degrees east or west of north, it is called a “quadrant bearing.”
If direction is expressed in degrees between 0 and 360, it is called “azimuth bearing.”

7. Quadrant Bearing
N22oE
What is the bearing from C to D?

8. Azimuth Bearing

9. General Information
Map Scale: Maps come in a variety of scales, covering areas ranging from the entire earth to a city block (or less).
Vertical Scale (contour interval): All maps have a horizontal scale. Topographic maps also have a vertical scale to allow the determination of a point in three dimensional space.
Contour Lines: Contour lines are used to determine elevations and are lines on a map that are produced from connecting points of equal elevation (elevation refers to height in feet, or meters, above sea level).

10. Rules for Contour Lines

11. Rules for Contour Lines

12. Rules for Contour Lines

13. Rules for Contour Lines

14. Contour lines on ridges and valleys

15. Contour lines on closed depressions

16. Contour Interval
The Contour Interval (CI) is the difference in elevation between two adjacent contour lines.
The CI can vary from map to map. Usually expressed in feet or meters.
Elevation is always referenced to Mean Sea Level (MSL).
MSL=0

17. Map Scale several representations of scale exist
Verbal: “one inch equals one mile”
Ratio: 1:24,000 means that the portion of the earth represented has been reduced to 1/24000th its actual size.
Graphic

18. Calculating Gradient (or Slope)
Change in elevation between 2 points
Distance between 2 points
Gradient =
Gradient is usually expressed as ft/mi.

19. Local Topographic Map (1984)

20. Aerial Photo (1988)

21. Aerial Photo (1995)

22. Aerial Photo (2002)

23. Topographic Profiles
topographic maps represent a view of the landscape as seen from above (called “map view”)
for producing a detailed study of a landform it is necessary to construct a topographic profile
a topographic profile is a cross-sectional view along a line drawn through a portion of a topographic map

24. Creating topographic profiles
Lay a strip of paper along a line across the area where the profile is to be constructed.
Mark on the paper the exact place where each contour, stream and hill top crosses the profile line.
Label each mark with the elevation of the contour it represents.

25. Creating topographic profiles
Prepare a vertical scale on profile paper by labeling the horizontal lines corresponding to the elevation of each index contour line.
Place the paper with the labeled contour lines at the bottom of the profile paper and project each contour to the horizontal line of the same elevation.
Connect the points.

26. Creating topographic profiles

27. Creating topographic profiles

28. Creating topographic profiles

29. Vertical Exaggeration
Vertical Scale
Horizontal Scale
VE =
Example: VE = 1:2000/1:4000= 2, which basically means... "the vertical relief of the terrain portrayed in this profile view is exaggerated two-fold relative to its actual profile in the real-world".

30. Vertical Exaggeration