Topographic Maps Tutorial

Introduction & Materials

What is a Map?

Using Topo Maps

Map Scale

Reference Datum

Map Projections

Distortions

Grid Systems

Geographic

UTM

State Plane

Public Land Survey

Vertical Scale

Creating Profiles

Vertical Exaggeration

Calculating Slope

Using a Compass

Magnetic Declination

Get a Bearing

Go from A to B

Find Self on a Map

Topographic Maps Field Exercises

Exercise 1

Exercise 2

Exercise 3

Exercise 4

GeoSTAC Home

Field Exercises

geostac@gmail.com

April 7, 2008

Exercise Three

Purpose: Gain an understanding of how linear 'map distances' vary from non-linear 'ground-distances', and how travel speeds vary as a result of topography and vegetation. Much of this may seem intuitive, but it is important to get a real understanding of how these factors influence your ability to travel, especially if you are planning a hike or estimating the time it will take you to get from point A to point B.

Before going into the field choose two areas on the map where you can draw a straight line, equal in distance to a mile at the scale of the map. Make one of the lines go through an area of relatively high topographic relief and the other through an area of relatively low topographic relief. If possible, draw your lines so they go through areas both with and without trees (trees are represented by shaded areas on the map). If you can’t make one line go through areas with and without trees, make one line in the trees and the other line out of the trees. Record the starting and ending points of your profile lines using both UTM and Geographic coordinates.

Draw a topographic profile along each of your lines with no vertical exaggeration. Included on your profile should be: a scale, vertical axis labels, and directional labels (E-W, N-S, etc.).

Using a ruler, measure the length of the line that makes up your topographic profile. Although it will not be exact, you can estimate the total length by summing the distance between each of the points you used to create your profile. This will give you the true 'ground distance' of your line. For each of your profiles, what is the difference between the straight-line 'map distance' and the true 'ground distance' in feet and meters? What is the percent difference (i.e. the ground distance is "Z"% greater than the map distance).

Calculate the average slope for each section of your profiles (i.e. calculate the slope separately for each uphill and downhill section of the profile).

Find a relatively flat, open section of ground near where you live where you can measure off a mile accurately (a running track would be ideal).

Time yourself while walking one mile at your normal pace, and record your result.

Estimate, based on your time in the mile, how long you think it will take you to walk each of your profile lines.

Go into the field and time yourself walking, in as straight a line as possible, each of your profile lines. Note the elapsed time every time you encounter a major change in slope (at the top and bottom of each hill).

Record your total time and, on your profile, record the amount of time it took you to complete each uphill and downhill section.

Turn in a brief write up that includes your profiles and the answers to the questions posed above, as well as discussing the following:

• How far off from your estimated time was your actual time?
• Do you think you made up as much time going downhill as you lost going uphill?
• What slowed you down more, topography or vegetation?
• Was it difficult to walk in a straight line?
• Why or why not (discuss any difficulties encountered)?
• Using your 20/20 hindsight, are there clues on the map that could have helped you choose an easier and/or quicker route to get to your destination?

Continue to Exercise Four . . .