Map Projections

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Map Projections

• used to transfer the image of the earths surface
  onto a flat surface
• no projection is an exact representation
• generally, the larger the area, the larger the
  distortion
• the 3 most common projections are cylinders,
  cones and planes

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Cylindrical Projections
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Mercator Projections

• results when the contents of a globe are
  transferred onto a cylinder of paper

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Conic Projections

• made by transferring the contents of a globe onto
  a cone
• distortion increases north to south
• best used for land masses that have more area
  east to west (USA) than north to south (South
  America)

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Planar Projections
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Azimuthal Projections

• made by transferring the contents of a globe onto
  a plane
• the plane touches the globe
• at only 1 point, usually at
• the poles
• very little distortion at that point
• distortion of direction, distance and shape
  increase as the distance from the point of
  contact increases

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West Wing Map Projection Clip

• http//www.youtube.com/watch?vn8zBC2dvERM

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Modern Map Making
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Aerial Photographs

• taken from planes
• are very important to map makers in making
  accurate maps
• allow for a different perspective

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Remote Sensing

• the gathering of information about a place
  without being there
• cameras in planes, satellites with sensors
• allow for very accurate maps

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Information shown on maps
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Title

• tells what area is being shown on the map or
  gives information about the map subject
• A Map of the Coast of East Florida from the River
  St. John Southward near to Cape Canaveral 1791
• A Map of the New Governments of East and West
  FLORIDA. Inset of Pensacola 1763
• A map of the peninsula of Florida showing the
  present field of surveying in the territory -
  1846
• A Map of the Southern Indiana District of North
  America - - - Manuscript in Ayer Collection at
  the Newberry Library 1775
• A Map of the WEST INDIES... - 1715

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Maps scale

• shows the relationship between the distance on
  the earths surface and the distance on the map

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Graphic scale ? maps ruler

• the distance on the earths surface is
  represented by a bar graph that shows units of
  distance

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Verbal scale

• is a phrase that describes a measure of distance
  on a map relative to the distance on the earths
  surface

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Representative fraction

• a fraction or ratio that shows the relationship
  between the distance on the map and the distance
  on the earths surface

• it is unitless

• it remains constant no matter the measurement used

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Compass rose

• shows how the map is positioned in relation to
  true north

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Legend

• is a list of symbols used on the map and their
  explanations

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Date

• gives the time at which the information on the
  map was accurate
• County Map of Florida - 1872
• County Map of Florida - 1882

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Topographic map

• a map that shows surface features (topography) of
  the Earth

• natural features like rivers, lakes, mountains

• man made features like cities, roads, bridges

• also show elevation

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Elevation

• the height of an object above sea level
• sea level is 0

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Topographic maps of the entire US were prepared
by the Unites States Geological Survey (USGS)
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Contour lines

• are lines that connect points of equal elevation

• are used to show elevation

• the closer the contour lines, the steeper the
  slope

• the more spread out the contour lines, the
  flatter the slope

• contour lines never intersect

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contour interval

• the difference in elevation between contour lines

• contour interval is chosen according to the
  areas relief

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relief

• the difference in elevation between the highest
  point and the lowest point being mapped

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index contour

• a darker, heavier contour line (usually every 5th
  line) that is labeled by elevation
• makes reading the map easier

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hachures

• short, straight lines within a contour line
• indicate a depression

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Reading a Topographic Map
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Step 1

• Contour lines never cross all points along
  a contour line are of the same elevation

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Step 2

• Closely spaced contour lines indicate a very
  steep slope widely spaced contour lines indicate
  a subtle slope

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Step 3

• Contour lines crossing valleys or streams
  are V shaped. The V points to the higher
  elevation. If there is a river or stream in the
  valley, the V indicates the upstream direction.

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Step 4

• Contour lines formed closed loops around hills,
  mountains and depressions.
• Check for hachures.