Interpretation and Construction of Topographic Maps Interpretation

Goals of the Topographic Map Interpretation Lab Understand how surface features are expressed on the earth’s surface Observe a 2-dimensional map and “convert” it to a 3-dimentional relief map Locate geographical positions using the PLSS system (a legal description) Students will understand the nature of contour lines and how contour lines can determine: surface features river gradients map relief and elevation Develop skills that enable the student to construct topographic maps and topographic profiles Goals of the Topographic Map Interpretation Lab Understand how surface features are expressed on the earth’s surface Observe a 2-dimensional map and “convert” it to a 3-dimentional relief map Locate geographical positions using the PLSS system (a legal description) Students will understand the nature of contour lines and how contour lines can determine: surface features river gradients map relief and elevation Develop skills that enable the student to construct topographic maps and topographic profiles 1 st Lab 1 st Lab 2 nd Lab 2 nd Lab

Topographic Map Lab Types of maps Planimetric Maps – a typical road map with cities Topographic Maps – a planimetric map as well as a 3-d representation of the “lay of the land” converts a 2-D to a 3-D map “lay of the land” converts a 2-D to a 3-D map Types of maps Planimetric Maps – a typical road map with cities Topographic Maps – a planimetric map as well as a 3-d representation of the “lay of the land” converts a 2-D to a 3-D map “lay of the land” converts a 2-D to a 3-D map Shows streets, roadways “sometimes not very accurate” Shows streets, roadways “sometimes not very accurate” Shows accurate scaling, elevation and geographic locations. Shows accurate scaling, elevation and geographic locations. elevations

What can one do with a Topographic Map Calculate river gradients Hiking- how rigorous is the trail Hunting – where would game hang out? Navigate your way Interpret various geological features

Interpreting SCALE on a topographic map Representative Fraction Scale (RF scale) Graphic Bar Scale (graphical representation) Verbal Scale (what does the map say?) Interpreting SCALE on a topographic map Representative Fraction Scale (RF scale) Graphic Bar Scale (graphical representation) Verbal Scale (what does the map say?) Model (Map size) Actual Size 1:18 scale 1:1 scale feet Graphically shows distance Graphically shows distance “What is the map telling you???”

Representative Fraction Scale (RF scale) the “ratio scale” or “unitless scale” 1 : 24,000 or 1/24,000 – can apply any units (:) or (/) means equal (=) How does this scale work? (let’s use inches and the scale of 1:24,000 Representative Fraction Scale (RF scale) the “ratio scale” or “unitless scale” 1 : 24,000 or 1/24,000 – can apply any units (:) or (/) means equal (=) How does this scale work? (let’s use inches and the scale of 1:24,000 1 map inch = 24,000 real earth inches OR 1 map inch = 2000 feet OR 1” = 2000 feet 1 map inch = 24,000 real earth inches OR 1 map inch = 2000 feet OR 1” = 2000 feet 1:24,0001:5,0001:10001:525,000 Which scale shows more map detail?

Graphic Bar Scale: graphical representation of distance Graphic Bar Scale: graphical representation of distance Kilometers Comparing a map distance (from point A to B) to the Bar scale (at the bottom of map) Comparing a map distance (from point A to B) to the Bar scale (at the bottom of map) What about a meandering river??? STRING

The Verbal Scale: The map “tells” you what the scale is (just listen?) Usually located at the bottom of the map ALL verbal scales should match the RF scale and bar scale Example: 1 inch equals 2000 feet The Verbal Scale: The map “tells” you what the scale is (just listen?) Usually located at the bottom of the map ALL verbal scales should match the RF scale and bar scale Example: 1 inch equals 2000 feet

Map Orientation – Where does your compass point ???? Magnetic Declination: True North (Santa Claus) vs. Magnetic North Magnetic Declination: True North (Santa Claus) vs. Magnetic North North (Santa Claus) X X Map points to TN Map points to TN Compass needle points to MN Compass needle points to MN EARTHEARTH Magnetic Declination (MD) The angle between TN and MN is the magnetic declination The angle between TN and MN is the magnetic declination TN MN MD Map Symbol Bakeo

MAP North South East West NEWS

R1E R2E R1W R2W R3W T1N T2N T1S Townships North/South Townships North/South Ranges East/West Ranges East/West Principal Meridian Base Line T2N R2E T2N R2E T1N R2E T1N R2E T1S R2E T1S R2E T2N R1E T2N R1E T1N R1E T1N R1E T1S R1E T1S R1E T2N R1W T2N R1W T1N R1W T1N R1W T1S R1W T1S R1W T2N R2W T2N R2W T1N R2W T1N R2W T1S R2W T1S R2W T2N R3W T2N R3W T1N R3W T1N R3W T1S R3W T1S R3W T2N, R2E miles 1 mile NW ¼ of NE1/4 NW ¼ of NE1/4 20 SW 1/4 of NE 1/4 SW 1/4 of NE 1/4 of NE 1/4 of NE 1/4 SE ¼ of NE 1/4 SE ¼ of NE 1/4 NW 1/4 SW 1/4 SE 1/4 T2N,R2E,Sec 20,1/4NE,1/4SW X X Sections

Creating a Topographic map with Contour Lines Contour line – a line that connects points of equal elevation equal points of elevation 5 important rules of contour lines 1.Contours line do not cross or divide 2. Contour lines will eventually close – they don’t stop 3. Steep slopes – contour lines are close together Gentle slopes – contour lines are widely spaced Gentle slopes – contour lines are widely spaced 4. Depressions shown with hachures pointing downward 5. Contour lines intersecting streams will always “V” in the upwards direction (streams flow through the open in the upwards direction (streams flow through the open “V”) “V”)

Contour lines never cross or divide Contour lines eventually close – Don’t stop

Close together contour lines = STEEP SLOPES Separated contour lines = GENTLE SLOPES Close together contour lines = STEEP SLOPES Separated contour lines = GENTLE SLOPES SteepSteep GentleGentle

Depressions are shown with hachures pointing inward inward Rivers always flow in the direction of the open “V” of a contour line Rivers always flow in the direction of the open “V” of a contour line WEST NORTH

The Contour Interval How many contour lines can fit in a determined Space??? Space??? The Index contour line – the “dark numbered” elevation line The contour interval – the amount of contour lines in-between the index contour lines The Index contour line – the “dark numbered” elevation line The contour interval – the amount of contour lines in-between the index contour lines Contour Interval = 20 CI = Contour Interval = 100 CI =

Calculating the gradient how steep is the slope?? how steep is the slope?? Calculating the gradient how steep is the slope?? how steep is the slope?? Rise Run Rise = highest elevation – lowest elevation Run = the length (distance) Rise and Run MUST be in the same units preferably “feet” Rise = highest elevation – lowest elevation Run = the length (distance) Rise and Run MUST be in the same units preferably “feet” Higher slope # = steeper

Making a Topographic Profile represents a “cross-section” or side view of represents a “cross-section” or side view of topography topography uses a horizontal and vertical scale uses a horizontal and vertical scale gives the map reader a “picture” of the “lay of gives the map reader a “picture” of the “lay of the land”. the land”. Making a Topographic Profile represents a “cross-section” or side view of represents a “cross-section” or side view of topography topography uses a horizontal and vertical scale uses a horizontal and vertical scale gives the map reader a “picture” of the “lay of gives the map reader a “picture” of the “lay of the land”. the land”. How do you make a Topographic profile ?

Lay a strip of paper over the topographic area Lay a strip of paper over the topographic area “Mark off” contour lines that intersect the paper “Mark off” contour lines that intersect the paper strip – recording their elevations strip – recording their elevations Intersecting contour lines

Remove strip of paper and place it on graph paper – plot elevation points (on strip) to paper – plot elevation points (on strip) to match vertical scale elevation points match vertical scale elevation points Remove strip of paper and place it on graph paper – plot elevation points (on strip) to paper – plot elevation points (on strip) to match vertical scale elevation points match vertical scale elevation points potting points on the graph paper Strip of paper

Outline the topography by “connecting” the dots --- Use your artistic ability to construct a “smooth” picture Outline the topography by “connecting” the dots --- Use your artistic ability to construct a “smooth” picture

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