Interpretation Interpretation and Construction of Topographic Mapsand Construction of Topographic Maps

Interpretation Interpretation and Construction of Topographic Mapsand Construction of Topographic Maps

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 featuresriver gradientsmap 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 featuresriver gradientsmap relief and elevation

• Develop skills that enable the student to construct topographic maps and topographic profiles

1st

Lab1st

Lab

2nd

Lab2nd

Lab

Topographic Map LabTopographic Map LabTopographic Map LabTopographic Map Lab

Types of maps Types of maps

Planimetric MapsPlanimetric Maps – a typical road map – a typical road map with with cities cities

Topographic MapsTopographic Maps – a planimetric map as – a planimetric map as well as well as a 3-d representation a 3-d representation of the of the

“ “lay of the land” converts lay of the land” converts a a 2-D to a 3-D map 2-D to a 3-D map

Types of maps Types of maps

Planimetric MapsPlanimetric Maps – a typical road map – a typical road map with with cities cities

Topographic MapsTopographic Maps – a planimetric map as – a planimetric map as well as well as a 3-d representation a 3-d representation of the of the

“ “lay of the land” converts lay of the land” converts a a 2-D to a 3-D map 2-D to a 3-D map

Shows streets, roadways“sometimes not very accurate”Shows streets, roadways“sometimes not very accurate”

Shows accurate scaling, elevationand geographic locations.Shows accurate scaling, elevationand geographic locations.

elevations

What can one do with a Topographic MapWhat can one do with a Topographic Map

Calculate river gradientsCalculate river gradients

Hiking- how rigorous is the trailHiking- how rigorous is the trail

Hunting – where would game hang Hunting – where would game hang out?out?

Navigate your wayNavigate your way

Interpret various geological Interpret various geological featuresfeatures

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 SizeActual Size1:18 scale

1:1 scale1:1 scale

5050 100100 150150 200200

feetfeetGraphically shows distanceGraphically shows distance

“What is the map telling you???”“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 inchesOR

1 map inch = 2000 feetOR

1” = 2000 feet

1 map inch = 24,000 real earth inchesOR

1 map inch = 2000 feetOR

1” = 2000 feet

1:24,000 1:5,000 1:1000 1:525,0001:24,000 1:5,000 1:1000 1:525,000

Which scale shows more map detail?Which scale shows more map detail?

Graphic Bar ScaleGraphic Bar Scale:: graphical representation of distancegraphical representation of distance Graphic Bar ScaleGraphic Bar Scale:: graphical representation of distancegraphical representation of distance

00 44KilometersKilometers

00 11 22 33 44

Comparing a map distance (from point A to B) to theBar scale (at the bottom of map)Comparing a map distance (from point A to B) to theBar scale (at the bottom of map)

What about a meandering river???What about a meandering river???

STRINGSTRING

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 ????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)North (Santa Claus)North (Santa Claus)North (Santa Claus)

XXMap pointsto TNMap pointsto TN

Compass needlepoints to MNCompass needlepoints to MN

EARTHEARTHEARTHEARTH

Magnetic Declination (MD)Magnetic Declination (MD)Magnetic Declination (MD)Magnetic Declination (MD)

The angle between TN and MN is the magnetic declinationThe angle between TN and MN is the magnetic declination

TNTNMNMN

MDMDMap SymbolMap SymbolMap SymbolMap Symbol

BakeoBakeo

MAPMAP

NorthNorth

SouthSouth

EastEastWestWest

NEWSNEWS

R1ER1E R2ER2ER1WR1WR2WR2WR3WR3W

T1NT1N

T2NT2N

T1ST1S

TownshipsNorth/South

TownshipsNorth/South

RangesEast/West

RangesEast/West

Principal MeridianPrincipal Meridian

Base LineBase Line

T2NR2ET2NR2E

T1NR2ET1NR2E

T1SR2ET1SR2E

T2NR1ET2NR1E

T1NR1ET1NR1E

T1SR1ET1SR1E

T2NR1WT2NR1W

T1NR1WT1NR1W

T1SR1WT1SR1W

T2NR2WT2NR2W

T1NR2WT1NR2W

T1SR2WT1SR2W

T2NR3WT2NR3W

T1NR3WT1NR3W

T1SR3WT1SR3W

T2N, R2ET2N, R2E

6666 5555 4444 3333 2222 1111

7777 8888 9999 10101010 11111111 12121212

18181818 17171717 16161616 15151515 14141414 13131313

19191919 20202020 21212121 22222222 23232323 242424246 m

iles

6 m

iles

6 miles6 miles

1 m

ile

1 m

ile

1 mile1 mileNW ¼ of NE1/4

NW ¼ of NE1/4

2020

SW 1/4of

NE 1/4

SW 1/4of

NE 1/4

NE 1/4of

NE 1/4

NE 1/4of

NE 1/4

SE ¼of

NE 1/4

SE ¼of

NE 1/4

NW 1/4NW 1/4

SW 1/4SW 1/4 SE 1/4SE 1/4

T2N,R2E,Sec 20,1/4NE,1/4SWT2N,R2E,Sec 20,1/4NE,1/4SW

XXSectionsSections

252526262727282829293030

3131 3232 3333 3434 3535 3636

Creating a Topographic map with Contour LinesCreating a Topographic map with Contour Lines

Contour line – a line that connects points of equal elevationContour line – a line that connects points of equal elevation

equal points of elevationequal points of elevation

5 important rules of contour lines5 important rules of contour lines

1.1.Contours line do not cross or divideContours line do not cross or divide

2. 2. Contour lines will eventually close – they don’t stopContour lines will eventually close – they don’t stop

3. 3. Steep slopes – contour lines are close togetherSteep slopes – contour lines are close together Gentle slopes – contour lines are widely spacedGentle slopes – contour lines are widely spaced

4. 4. Depressions shown with hachures pointing downwardDepressions shown with hachures pointing downward

5. Contour lines intersecting streams will always “V” 5. Contour lines intersecting streams will always “V” in the upwards direction (streams flow through the openin the upwards direction (streams flow through the open

“ “V”)V”)

404040404040

4040

Contour lines never cross or divideContour lines never cross or divide

100100100100200200

Contour lines eventually close – Don’t stopContour lines eventually close – Don’t stop

500500500500

Close together contour lines = STEEP SLOPES

Separated contour lines = GENTLE SLOPES

Close together contour lines = STEEP SLOPES

Separated contour lines = GENTLE SLOPES

SteepSteepSteepSteepGentleGentleGentleGentle

Depressions are shown with hachures pointingDepressions are shown with hachures pointinginwardinwardDepressions are shown with hachures pointingDepressions are shown with hachures pointinginwardinward

Rivers always flow in the direction of theRivers always flow in the direction of theopen “V” of a contour lineopen “V” of a contour lineRivers always flow in the direction of theRivers always flow in the direction of theopen “V” of a contour lineopen “V” of a contour line

WESTWESTNORTHNORTH

The Contour IntervalThe Contour IntervalThe Contour IntervalThe Contour Interval

How many contour lines can fit in a determinedHow many contour lines can fit in a determinedSpace???Space???How many contour lines can fit in a determinedHow many contour lines can fit in a determinedSpace???Space???

The Index contour lineThe Index contour line – the “dark numbered” elevation line – the “dark numbered” elevation line

The contour intervalThe contour interval – the amount of contour lines – the amount of contour lines in-between the index contour linesin-between the index contour lines

The Index contour lineThe Index contour line – the “dark numbered” elevation line – the “dark numbered” elevation line

The contour intervalThe contour interval – the amount of contour lines – the amount of contour lines in-between the index contour linesin-between the index contour lines

200200

300300

Contour Interval = 20 Contour Interval = 20

CI = 20CI = 20

500500

Contour Interval = 100 Contour Interval = 100 CI = 100CI = 100

100100

Calculating the gradientCalculating the gradient• how steep is the slope??how steep is the slope??

Calculating the gradientCalculating the gradient• how steep is the slope??how steep is the slope??

Rise

Run

RiseRise = highest elevation – lowest elevation = highest elevation – lowest elevation

Run = the length (distance) Run = the length (distance)

Rise and Run Rise and Run MUSTMUST be in the same units be in the same unitspreferably “feet”preferably “feet”

RiseRise = highest elevation – lowest elevation = highest elevation – lowest elevation

Run = the length (distance) Run = the length (distance)

Rise and Run Rise and Run MUSTMUST be in the same units be in the same unitspreferably “feet”preferably “feet”

Higher slope # = steeper Higher slope # = steeper

Making a Topographic ProfileMaking a Topographic Profile

• represents a “cross-section” or side view ofrepresents a “cross-section” or side view of topographytopography

• uses a horizontal and vertical scaleuses a horizontal and vertical scale

• gives the map reader a “picture” of the “lay ofgives the map reader a “picture” of the “lay of the land”.the land”.

Making a Topographic ProfileMaking a Topographic Profile

• represents a “cross-section” or side view ofrepresents a “cross-section” or side view of topographytopography

• uses a horizontal and vertical scaleuses a horizontal and vertical scale

• gives the map reader a “picture” of the “lay ofgives the map reader a “picture” of the “lay of the land”.the land”.

How do you make a Topographic profile ?How do you make a Topographic profile ?How do you make a Topographic profile ?How do you make a Topographic profile ?

• Lay a strip of paper over the topographic areaLay a strip of paper over the topographic area

• “ “Mark off” contour lines that intersect the paperMark off” contour lines that intersect the paper strip – recording their elevationsstrip – recording their elevations

Intersecting contour linesIntersecting contour lines

• Remove strip of paper and place it on graphRemove 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 pointsmatch vertical scale elevation points

• Remove strip of paper and place it on graphRemove 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 pointsmatch vertical scale elevation points

potting points on the graph paperpotting points on the graph paperpotting points on the graph paperpotting points on the graph paper

Strip of paperStrip of paperStrip of paperStrip 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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