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The Science of Geography and Maps


... Globe to ... of a globe, not the least of which is that a globe doesn't fold ... a piece of paper into a cone shape and placing it over one pole of the globe. ... – PowerPoint PPT presentation

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Title: The Science of Geography and Maps

The Science of Geography and Maps
  • Dr. R. B. Schultz

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

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
  • North-South lines are called Longitude or
  • East-West lines are called Latitudes or Parallels.

  • 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.

  • 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 hardly ever perfectly square (except at the

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
  • Every location on Earth is measured based on
    degrees north and south of the equator and east
    or west of the Prime Meridian.

From Globe to a Flat Map
  • 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.

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

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.

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

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

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

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.

Remote Sensing Techniques
  • Remote sensing is the science of remotely
    acquiring, processing, interpreting and
    presenting spatial data for objects and
    environmental processes 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).

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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The Geographic Information System (GIS)
  • Simply put, a GIS combines layers of information
    about a place to give you a better understanding
    of that place.
  • 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//

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

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

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.

  • 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
  • Since many monuments have been lost or destroyed
    over the years, retracement surveys are conducted
    to re-establish previously surveyed boundary
  • New, sturdy monuments are placed where the old
    monuments were located, at the specified corners.

How the PLS System Works
  • The basis for the PLS is the Congressional
  • 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
  • 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
  • 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.

  • 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

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