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## The Science of Geography and Maps

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### ... 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

1
The Science of Geography and Maps
• Dr. R. B. Schultz

2
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

3
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.

4
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.

5
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 hardly ever perfectly square (except at the
equator).

6
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.

7
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.

8
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.

9
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.

10
Conic Projection
• Imagine wrapping a piece of paper into a cone
shape and placing it over one pole of the globe.

11
Planar Projection
• Imagine using a piece of paper to trace the
details of one side or pole of the Earth.

12
Oval Projection
• Probably the most commonly used map projection,
it strives to even out distortions both near the
poles and near the equatorial regions.

13
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.

14
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).

15
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)

16
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17
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//www.esri.com/company/gis_touches/everyday.h
tml

18
Simple GIS Layers
19
Complex GIS Layers
20
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.

21
GPS satellites triangulate points on the Earths
surface.
22
Using remote sensing satellites in space, the GPS
system can locate points to within inches of its
actual location.
23
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.

24
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.

25
• 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 are placed where the old
monuments were located, at the specified corners.

26
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.

27
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28
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29
• 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.

30
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31
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.

32
• 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.

33
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
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