Geography and Mapping

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Geography and Mapping

• Dr. R. B. Schultz

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An Introduction to Geography

• One of the most useful functions of the science
  of geography is to determine the location of
  something.
• The two (2) most often used methods for
  designating location are
• Latitude and Longitude and
• The Public Land Survey System

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Latitude and Longitude

• By International convention, we use a system of
  north-south and east-west grid lines, although it
  is often cumbersome to use because of the
  irregular not quite spherical shape of the
  Earth.
• North-South lines are called Longitude or
  Meridians.
• East-West lines are called Latitudes or Parallels.

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Longitude

• Longitude lines are measured in degrees, minutes
  and seconds east or west of the Prime Meridian
  (located running through Greenwich, England).
• The 180-degree line of longitude is called the
  International Dateline.

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Latitude

• While lines of longitude converge at the poles,
  all lines of latitude are parallel.
• Therein lies the confusion, since the
  intersection of lines of longitude and latitude
  are never perpendicular (except at the equator).

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Lines of Reference

• On a large scale, the line of reference for
  longitude is the Prime Meridian.
• The line of reference for latitude is the
  equator.
• Every location on Earth is measured based on
  degrees north and south of the equator and east
  or west of the Prime Meridian.

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From Globe to a Flat Map

• As long as there have been maps, cartographers
  have grappled with the impossibility of
  portraying the earth in two dimensions. To solve
  this problem mapmakers have created hundreds of
  map projections mathematical methods for drawing
  the round earth on a flat surface.
• Yet of the hundreds of existing projections, and
  the infinite number that are theoretically
  possible, none is perfectly accurate.
• There are obvious reasons for wanting to work
  with a map instead of a globe, not the least of
  which is that a globe doesnt fold well.
• The difficult aspect of converting or
  projecting onto a flat surface is that it
  usually adds error called distortion.

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Map Projections

• Several classes of map projections exist for
  different purposes
• Mercator (cylindrical) Projection
• Conic Projection
• Planar or Gnomonic Projection
• Oval Projection
• Each has its own purpose and is useful for
  various tasks.

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Mercator Projection

• Imagine wrapping a piece of paper around a globe
  and tracing where the paper touches the surface.
  That is essentially a Mercator Projection.

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Conic Projection

• Imagine wrapping a piece of paper into a cone
  shape and placing it over one pole of the globe.

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Planar Projection

• Imagine using a piece of paper to trace the
  details of one side or pole of the Earth.

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Oval Projection

• Probably the most commonly used map projection,
  it strives to even out distortions both near the
  poles and near the equatorial regions.

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New Mapping Technologies

• With the advent of new technologies, more
  accurate maps are constructed and at a much
  faster rate than in the olden days of
  hand-drawn maps.
• Recent technologies include Remote Sensing.

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Remote Sensing Techniques

• Remote sensing is the science of remotely
  acquiring, processing, interpreting and
  presenting spatial data for objects using signals
  from a broad range within the electromagnetic
  spectrum.
• Remote sensing instruments are able to produce
  images of the physical properties and
  characteristics of objects without being in
  physical contact with them (e.g., remotely)
• Instead, this highly advanced technology forms
  images by gathering, focusing, and recording
  reflected light from the sun, energy emitted by
  the object itself, or reflected radar waves
  (which were emitted by the satellite or other
  remote sensing devices).

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Remote Sensing Techniques

• Remote sensing techniques include, but are not
  limited to
• Space shuttle
• LANDSAT series satellites
• Orbital sensors
• High- and medium-altitude aircraft
• Earthbound sensors
• Maritime Remote Sensors (onboard ships)

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How is Remote Sensing Accomplished?
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The Geographic Information System (GIS)

• Simply put, a GIS combines layers of information
  about a place to give you a better understanding
  of it.
• What layers of information you combine depends on
  your purposefinding the best location for a new
  store, analyzing environmental damage, viewing
  similar crimes in a city to detect a pattern, and
  so on.
• See this web site for how GIS affects ALL of us
  http//www.esri.com/company/gis_touches/everyday.h
  tml

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Simple GIS Layers
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Complex GIS Layers
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The Global Positioning System

• Currently, we use the Global Positioning System
  (GPS) to aid in the location of points or
  structures.
• It is centered on satellite imagery (a type of
  remote sensing) and can very accurately locate a
  point on the Earth.

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GPS satellites triangulate points on the Earths
surface.
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Using remote sensing satellites in space, the GPS
system can locate points to within inches of its
actual location.
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The Public Land Survey System

• Because GPS and GIS systems are so new and not
  fully incorporated into the mainstream, the U.S.
  currently uses a rather outdated and archaic
  system to locate points.
• The Public Land Survey (PLS) System is more
  accurate, however, than Longitude and Latitude on
  a small-scale basis.

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The Public Land Survey System

• The Public Land Survey System (PLSS) is a legal
  land reference system set up to ease the
  inventory and transfer of property.
• The original PLSS surveys were conducted over 100
  years ago. The task of present-day land
  surveyors, includes the retracing of the original
  lines, and further subdividing sections.
• Today almost all land transactions in the 30
  western-most states are described with this
  section, township, and range system.

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• The position of a PLSS corner, a corner of a
  township or a corner of one of it's 36 sections,
  is defined by the original monument, and whether
  or not it's placement was mathematically correct.
  
• Many early monuments were made of wood, stone or
  other natural materials susceptible to decay and
  destruction.
• Since many monuments have been lost or destroyed
  over the years, retracement surveys are conducted
  to re-establish previously surveyed boundary
  lines.
• New, sturdy monuments made of brass plates are
  placed where the old monuments were located, at
  the specified corners.

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How the PLS System Works

• The basis for the PLS is the Congressional
  Township.
• It is 36 square miles (6 miles wide by 6 miles
  high) and defined by Tiers (analogous to lines of
  latitude) and Ranges (analogous to lines of
  longitude).
• Each square mile is termed a section so there
  are 36 sections in a Township.

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• Sections are also divided up into quarters (each
  being ¼ square mile).
• Quarters can then be divided up into
  quarter-quarters, which can then be divided into
  quarter-quarter-quarters, and so on.

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PLS Notation

• Now that we know the PLS by definition, we must
  know how to write it in the standardized
  notation.
• By convention we read (and write) left to right.
• In the PLS, we also read (and write) left to
  right with the smallest parcel (tract) of land to
  the left and largest to the right.
• An example would be
• SW1/4,NE1/4, sec. 12, T. 4 N., R. 6 E.
• Smallest ------------------------------Largest

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• Besides being able to look at a location and find
  it on a map, we must also be able to find a
  location on a map and write the PLS notation for
  it.

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Key Terminology

• Meridians Parallels
• Prime Meridian International Dateline
• Equator Projection
• Distortion Mercator
• Conic Planar
• Oval Remote Sensing
• Electromagnetic spectrum GIS
• Public Land Survey System Tier
• Range Section
• Quarter Congressional Township