typesofmapsandtopo.ppt

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Mapping The Earth’s Surface

• Maps are flat models of a

three-dimensional object, Earth.

• All flat maps distort to some degree either the shapes or the areas of landmasses.

• Cartographers use projections to make maps.

– A map projection is made by transferring

points and lines on a globe’s surface onto a

sheet of paper.

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Mercator Projection

Mercator_Mercator- a map projection in which both the _{- a map projection in which both the}

meridians (evenly spaced) and parallels (unevenly

spaced) are straight and parallel, forming a grid. Use to

be used for navigation. Normally used for areas near

the equator

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Gnomonic Projection

Gnomonic

Gnomonic- parallels appear unevenly spaced, - parallels appear unevenly spaced, concentric circles;

concentric circles; meridians_meridians appear as straight appear as straight lines radiating from a central point; all great circles

lines radiating from a central point; all great circles

appear as straight lines.

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Conic Projections

•Conic_Conic- meridians _{- meridians}

converge at the poles; the

parallels appear as equally

spaced, concentric curves

spaced, concentric curves •Polyconic Projection_{Polyconic Projection}- -

several conic projections

put together to form a

larger map

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Map Reading

• Legend- the portion of a

map that lists all symbols and their meanings,

distances, and intervals; aides map reading

• Map Direction- maps are usually drawn with north at the top of the page and

south at the bottom

• Scale- the comparison of the distance on the map to the actual distance covered

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Topographic Maps

• Topographic Map- scientific maps that show

surface features (such as mountains and

valleys) by using contour intervals; changes 3D

into 2D

– Topographic maps use lines, symbols, and colors to represent changes in elevation and features on Earth’s surface.

– Topography- surface features of the earth

• Elevation- the height, in feet or meters, above

or below sea level

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Making Topo Maps

• Contour Lines-lines on a map that connect points of the same elevation

• Contour Interval- the difference (in feet or meters) from one contour line to the next

• Relief- the change in elevation from the lowest to the highest points of an area; sometimes referred to as vertical relief

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Section Assessment

Match the following terms with their

definitions.

___ projection

___ contour interval ___ map scale

___ map legend

A. the difference in elevation between two side-by-side contour lines

B. a diagram that explains what the symbols on a map represent

C. a map made by transferring points and lines on a globe’s surface onto a sheet of paper

D. the ratio between distances on a map and actual distances on the surface of Earth

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TOPOGRAPHIC MAPS

• Topo maps that show elevation above sea level with contour lines.

• Contour lines are lines that connect points of equal elevation.

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What you see on a Topo

• The Contour interval is the change in elevation between isolines.

• This varies from map to map and is always listed in the key.

• Distance: A key is usually provided giving a scale, where 1 inch is equal to a set distance. • The compass direction on contour maps is

provided using a compass rose.

• Man made objects are also displayed on

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Topographic Map Rules

!

• 1) Isolines NEVER cross!!!! The lines connect points of equal value!!

• 2) Moving from one regular contour line to another ALWAYS represents a change in elevation

• 3) On a hill with a consistent slope, there are ALWAYS four intermediate contours for every index contour.

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• A series of

closed contours (the contours make a circle) represents a hill. • If the closed

contours are hachured it indicates a closed

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Depression Contours

–Depression contour lines are used to represent features that are lower than the surrounding area.

–On a map, depression

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The Rule of V’s

• Contour lines

crossing a stream valley will form a "V" shape pointing in

the uphill (and

upstream) direction. • Think of the V as

being an arrow pointing in the

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TOPOGRAPHIC

PROFILES

• To determine what the actual land

shape would be

• 1) First lay a strip of paper along the line that you wish to turn into a profile

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COMPLETING THE PROFILE

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Completed Profile:

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Calculating a Slope

• 1) Decide on an area for which you want to

calculate the slope (note, it should be an area where the slope direction does not change; do not cross the top of a hill or the bottom of a valley).

• 2) Once you have decided on an area of interest, draw a straight line perpendicular to the contours on the slope. For the most accuracy, start and end your line on, rather than between, contours on the map. • ₃₎ _{Measure the length of the line you drew and,}

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•

4)

Determine the total elevation

change along the line you drew

(subtract the elevation of the lowest

contour used from the elevation of the

highest contour used).

– You do not need to do any conversions on this measurement, as it is a real-world

elevation change.

•

5)

To calculate the angle of the slope,

divide the elevation change in feet by

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The elevation of Raleigh is 282 feet. The elevation at Morganton is 1634 feet.

What is the gradient in feet/mile?

Distance between the two cities is 115 miles. Show all work.

gradient = change in elevation

distance

= 1634 ft -282 ft

115 miles

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The elevation of Whiteville is 99ft.

The elevation at Lumberton Hill is 144ft. What is the gradient in ft/mi?

The distance between the two cities is 75 miles. Show all work.

gradient = change in elevation

distance

= 144ft– 99ft

75 mi

= 45 ft

75 mi