Topographic Maps

A. Topographic Maps 1. Topographic Map: a map that shows the elevation of an area by using special isolines called contour lines. 2. Isolines: are lines that are drawn on a map that connect all of the points on the map that have the same value.

A. Topographic Maps 3. Contour lines: are isolines that are drawn on an topographic map. a) These lines connect all points with the same elevation.

A. Topographic Maps b) Notice that isolines are drawn every 20 m to connect points with equal elevation. Notice that the contour lines drawn at 100, 200 & 300 m are darker than the others. These are special contour lines called index contour lines.

B. Topographic Map Rules 1. When contour lines are far apart that usually indicates that the area is flat or has a gentle slope. a) Elevation is changing very slow. b) Circle the area (in purple) with a gentle slope.

B. Topographic Map Rules 2. When contour lines are close together that usually indicates that the area is steep slope a) Elevation is changing very fast. b) Circle the area (in red) with a steep slope.

B. Topographic Map Rules 3. Contour lines bend upstream at the points where they cross a river. a) Since contour lines must only connect points at the same elevation, they must bend when they cross riverbeds. b) The contour lines bend in the opposite direction as the flow of the river.

B. Topographic Map Rules c) Use a green color pencil to show lines bending of the contour lines and the direction of the Mill River must be northeast.

B. Topographic Map Rules 4. Closed, unmarked circles inside each other indicate a hill. a) Small hills can be located on a topographic map by looking for areas where the contour lines connect together and form circles. b) As the circles get smaller, the elevation is getting higher. c) Hill contour lines are smooth and not marked with tiny lines (see next rule).

B. Topographic Map Rules d) On your map, find the three hills (in blue) and label it, “hill.” e) On your map, mark the elevation of the hill next to where you labeled it. f) On your map, mark the elevation range for each of the hills.

B. Topographic Map Rules g) Hill #1: Elevation = 220 m Elevation Range: Minimum Elevation= 221m Elevation Range: Minimum Elevation= 221m Elevation Range: Maximum Elevation= 239 m Elevation Range: Maximum Elevation= 239 m

B. Topographic Map Rules h) Hill #2: Elevation = 320 m Elevation Range: Minimum Elevation= 321 m Elevation Range: Minimum Elevation= 321 m Elevation Range: Maximum Elevation= 339 m Elevation Range: Maximum Elevation= 339 m

B. Topographic Map Rules i) Hill #3: Elevation = 380 m Elevation Range: Minimum Elevation= 381 m Elevation Range: Minimum Elevation= 381 m Elevation Range: Maximum Elevation= 399 m Elevation Range: Maximum Elevation= 399 m

B. Topographic Map Rules 5. Depressions are shown by small marks on a closed contour line. a) Draw the arrow and the depression marks (in red) in the map below. b) The arrow is pointing to a depression, or hole. c) The contour line with the marks, or hatchers, has the same elevation as the contour line before it.

B. Topographic Map Rules d) In this case the hatchered line has a value of 140 m, and the depression must be less than 140 m.

C. Topographic Map Profiles 1.Profile: a picture of what the landscape would look like from the side. a)It is a cross section of the landscape. 2.Given the topographic map below, which of the four choices below accurately depicts the correct profile between points X and Y? a)Identify a profile:

C. Topographic Map Profiles b)The best way to approach this is by the process of elimination. First of all, point X appears to be approximately 290 meters in elevation. Let's eliminate all the choices that don't begin at 290 meters:

C. Topographic Map Profiles b)The best way to approach this is by the process of elimination. First of all, point X appears to be approximately 300 meters in elevation. Let's eliminate all the choices that don't begin at 290 meters:

C. Topographic Map Profiles c)Next, we look at point Y, which appears to be approximately 130 meters.

C. Topographic Map Profiles

3)Drawing a Profile a)Given the topographic map at left, let’s draw a profile map from point P to point Q. b)First, we need a horizontal grid that represents the distance from P-Q c)Place an X every spot that your horizontal grid line touches a contour line. d)Use a ruler to transfer the points from the contour map to the grid. e)Then connect the points with a smooth line to draw the profile.

C. Topographic Map Profiles