Topographic MapsTopographic Maps

Essential QuestionsEssential Questions What do topographic maps depict?What do topographic maps depict?

How are they constructed?How are they constructed?

What are contours and isopleths?What are contours and isopleths?

How can they be used to understand the Earth, How can they be used to understand the Earth, and Earth processes?and Earth processes?

What’s the difference between a topographic map What’s the difference between a topographic map and a bathymetric map?and a bathymetric map?

Can other data sets be contoured?Can other data sets be contoured?

TopographyTopography

How maps show topographyHow maps show topography• HachureHachure• IsoplethsIsopleths• Hypsography (water flows)Hypsography (water flows)• ShadingShading• ContoursContours

Hachure

Isopleths & Hill Shading

Hypsography (water flows)

Contours

Contour LinesContour Lines

All points along a contour line are the All points along a contour line are the same elevation.same elevation.

Contour IntervalContour Interval is the elevation is the elevation change between adjacent contour change between adjacent contour lines.lines.

Most maps have Most maps have majormajor contour lines contour lines at a regular interval that are labeled at a regular interval that are labeled with their elevation.with their elevation.

Contour PropertiesContour Properties

The closer together the contour lines, The closer together the contour lines, the steeper the slope.the steeper the slope.

The The fall linefall line, or “straight down the , or “straight down the hill” is perpendicular to the contour hill” is perpendicular to the contour lines. This is the direction water lines. This is the direction water would flow.would flow.

Water flows downhill and is a major Water flows downhill and is a major force in shaping the topography.force in shaping the topography.

Understanding Contour LinesUnderstanding Contour Lines

The key to making contour lines The key to making contour lines useful is learning how to translate useful is learning how to translate from the “bird eye view” on the map, from the “bird eye view” on the map, to what you see and experience as to what you see and experience as you hike through the terrain.you hike through the terrain.• What will you see?What will you see?• Will you be going uphill or down?Will you be going uphill or down?• How steep will it be?How steep will it be?• How will these things change as you How will these things change as you

move along your path?move along your path?

Recognizing Basic FeaturesRecognizing Basic Features

Hilltop, Mountain, PeakHilltop, Mountain, Peak Drainage, Canyon, ValleyDrainage, Canyon, Valley Bluff, CliffBluff, Cliff RidgeRidge Saddle, Pass, CutSaddle, Pass, Cut

What is the highlighted feature?How do you know?

What is the highlighted feature?It’s a hill top, summit, or peak.

How do you know?The small “circle” contourlines are high points.

What is the highlighted feature?How do you know?

What is the highlighted feature?It’s a saddle, or pass

How do you know?The “hourglass” shape withhigher terrain on either side.

What is the highlighted feature?How do you know?

What is the highlighted feature?Steep terrain, possibly cliffs

How do you know?Contour lines are very close together.

What is the highlighted feature?How do you know?

What is the highlighted feature?It’s a wide flat valleythat gently slopes up tothe NW.

How do you know?Contour lines are far apartTerrain rises on either sideWater runs down the middleHigher contour lines to the NW

What is the highlighted feature?How do you know?

What is the highlighted feature?It’s a ridge line.

How do you know?A string of summits all in a lineTerrain drops off onboth sides

What are the highlighted features?How do you know?

What are the highlighted features?Intermittent streams

How do you know?The blue line with dotsThe V like contour lineswith the “sharp” end pointing upslope and towards a summit

What is the highlighted feature?How do you know?

What is the highlighted feature?It’s a ridge or finger

How do you know?U or V shaped contour linespointing down slope.Terrain drops off on both sides.It’s between two drainages.

What is the highlighted feature?How do you know?

What is the highlighted feature?It’s a drainage

How do you know?V or U shaped contourspointing uphill.It “flows” into anotherstream or drainage