introduction to geospatial analysis - exploregeo.orgexploregeo.org/pdf/day1_geosba.pdffive...
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Introduction to
Geospatial Analysis
Dr. Emily A. Fogarty
SUNY Stony Brook
What is geography?
• The study of spatial variation
• How – and why – things differ from place to
place on the surface of the earth
• The study of how observable spatial
patterns evolved through time
Spatial variation: predominant religion
Why spatial variation exists: earthquakes
Changes over time: deforestation
What is geography?
• Geography is a spatial science
• Spatial behavior of people
• Spatial relationships between places
• Spatial processes that create or
maintain those behaviors and
relationships
Spatial behavior of people: population
Spatial relationships between places: trade
Spatial processes: commuting and
urban form
Five fundamental themes of geography
1) Location: the meaning of relative and
absolute position on the earth's surface
Sample terms: Latitude and longitude, site
and situation, direction, distance, scale
Skills: Map reading, identification
Questions: Where is ____? Where is ____
relative to where I am?
2) Place: the distinctive and distinguishing
physical and human characteristics of
locales
Sample terms: Physical and cultural
landscapes, sense of place
Skills: Description, compare and contrast
Questions: What does ____ look like?
Why? How is it different from ____?
Five fundamental themes of geography
3) Relationships within places: the
development and consequences of human-
environment relationships
Sample terms: Ecosystems, natural
resources, environmental pollution
Skills: Evaluation, analysis
Questions: What human-environment
relationships are occurring? How do they
affect the place and its inhabitants?
Five fundamental themes of geography
4) Movement: patterns and change in human
spatial interaction on the earth
Sample terms: Migration, diffusion,
globalization
Skills: Explanation, prediction
Questions: How has this spatial pattern
developed? Will it continue to change?
What does it mean for the places involved?
Five fundamental themes of geography
5) Regions: how they form and change
Sample terms: Formal vs. functional regions
Skills: Synthesis, application
Questions: How has this spatial pattern
developed? Will it continue to change?
What does it mean for the places involved?
Five fundamental themes of geography
http://en.wikipedia.org/wiki/Geography
Physical geography focuses on geography as an Earth science. It aims to understand the physical lithosphere,
hydrosphere, atmosphere, and global flora and fauna patterns (biosphere). Physical geography can be
divided into the following broad categories:
Human geography is a branch of geography that focuses on the study of patterns and processes that shape
human interaction with various environments. It encompasses human, political, cultural, social, and
economic aspects. While the major focus of human geography is not the physical landscape of the Earth
(see physical geography), it is hardly possible to discuss human geography without referring to the physical
landscape on which human activities are being played out, and environmental geography is emerging as a
link between the two. Human geography can be divided into many broad categories, such as:
http://en.wikipedia.org/wiki/Geography
Environmental geography is the branch of geography that describes the spatial
aspects of interactions between humans and the natural world. It requires an
understanding of the traditional aspects of physical and human geography, as
well as the ways in which human societies conceptualize the environment.
Environmental geography has emerged as a bridge between human and
physical geography as a result of the increasing specialization of the two sub-
fields.
Furthermore, as human relationship with the environment has changed as a
result of globalization and technological change a new approach was needed to
understand the changing and dynamic relationship.
Examples of areas of research in environmental geography include emergency
management, environmental management, sustainability, and political ecology.
Cartography studies the representation of the Earth's surface with abstract
symbols (map making). Although other sub-disciplines of geography rely
on maps for presenting their analysis, the actual making of maps is
abstract enough to be regarded separately.
Cartography has grown from a collection of drafting techniques into an
actual science.
A nautical chart of the Mediterranean Sea
from the second quarter of the 14th
century. It is the oldest original
cartographic artifact in the Library of
Congress. http://en.wikipedia.org/wiki/Cartography
Introduction to maps
What is a map?
• A generalized view of an area, usually some
portion of Earth’s surface, as seen from
above at a greatly reduced size
• Any geographical image of the environment
• A two-dimensional representation of the
spatial distribution of selected phenomena
Why make maps?
• To represent a larger area than we can see
• To show a phenomenon or process we can’t
see with our eyes
• To present information concisely
• To show spatial relationships
Represent a larger area
Show
what
we
can’t
see
Present info concisely
Show spatial
relationships
How do we read maps?
• Maps are selective views of reality
• Size of the map relative to reality (scale)
• What’s on the map (symbolization)
• Shape of the map (projection)
Map scale
• Ratio of the distance on the map to the
distance on the ground
• Scale is a fraction
• Larger area covered means larger
denominator
• Larger denominator means smaller fraction
• So a large-scale map covers a small area
Large-scale
Small-scale
Map scale
• Ratio of the distance on the map to the
distance on the ground
1. Graphic:
• Stays the same when photocopied
• Might not be right for the whole map
Map scale
1. Verbal:
1 inch equals 10 miles
• Easy to understand
• Can change if photocopied
Map scale
1. Representative fraction or ratio:
1:24,000
• Units don’t matter
• Can change if photocopied
Map symbolization
• Symbols are a code instead of text
• Three kinds: point, line, area
• Consider shape, size, orientation, pattern,
color, value
Point symbols
• Every symbol counts as one occurrence
• Qualitative points
– Indicate location
– Can also describe that location
• Quantitative points
– Show a distribution
– Indicate a value (graduated symbols)
Indicate location
Describe location
Show a distribution
Indicate a value
Line symbols
• One-dimensional
• Mostly taken for granted (borders, roads)
• Isolines connect same values
• Flow-line maps indicate value by width of
line
Isolines
(Contour
lines)
Flow-line maps
Area symbols
• Each territory or region has one value
• Differences in kind
• Differences in value
– Choropleth maps
– Usually, darker indicates more
• Cartograms distort area to show value
Differences in kind
Differences in kind
Differences in value
(Choropleth)
Cartogram
Topographic maps
• Also called quadrangles
• Nearly 54,000 for the U.S.
• Done by the US Geological Survey
(USGS) since 1897
• Map out the entire country in a standard
fashion
Topographic maps
• Till the 1940s, you climbed to the highest
point and plotted what you could see from
there
• Aerial photography after WWII
• Two overlapping photos are put in a
stereoscope
• 10 photos for each 7.5 minute map
Topographic maps
• Show 2D features, point, line and area;
also show 3D via contour lines
• Common symbols are in the appendix of
the text
• Note the contour interval at the bottom of
the map
Typical Graph This is an example of a typical graph we are all familiar with.
The graph is made up of different “points” with lines that connect the points.
Typical Graph Each point has two values:
The “X” value that runs along the horizontal “X” axis
The “Y” value that runs along the vertical “Y” axis
Y axis
X axis
Typical Graph X value is always stated first
Followed by the Y value
The “origin” is the point where the 2 axes intersect with a value of (0,0)
(0,0)
(3,8) Y
X
(9,5)
Typical Graph A point can also have negative (-) values
Negative X values are to the left of the origin (0,0)
Negative Y values are below the origin
X
Y
(-X,+Y)
(+X,-Y)
(+X,+Y)
(-X,-Y)
(0,0)
East West, North South on The Earth
Let the X axis be the Equator.
Let the Y axis be the Prime Meridian that runs through Greenwich outside of London.
Lat/Long are the 2 grid points by which you can locate any point on earth.
Y
X
East West, North South on the Earth
Let each of the four quarters then be designated by North or South and East or West.
N
S
E W
East West, North South on the Earth
The N tells us we’re north of the Equator. The S tells us we’re south of the Equator.
The E tells us that we’re east of the Prime Meridian. The W tells us that we’re west of the Prime Meridian.
(N, W) (N, E)
(S, W) (S, E)
East West, North South on the Earth
That means all points in North America will have a North latitude and a West longitude because it is North of the Equator and West of the Prime Meridian.
(N, W)
Prime Meridian
East West, North South on the Earth
What would be the latitude and longitude directions in Australia?
Prime Meridian
If you said South and East , you’re right!
What is Latitude? Latitude is the distance from the equator along the Y axis.
All points along the equator have a value of 0 degrees latitude.
North pole = 90°N
South pole = 90°S
Values are expressed in terms of degrees.
Y
X
90°S
90°N
What is Latitude?
Each degree of latitude is divided into 60 minutes.
Each minute is divided into 60 seconds.
Y
X
90°S
90°N
This is also true of longitude.
What is Latitude?
For Example:
40° 54′ 51.09″ N
This is close to the latitude where you live.
Y
X
90°S
90°N
What is Longitude?
Longitude is the distance from the prime meridian along the X axis.
All points along the prime meridian have a value of 0 degrees longitude.
The earth is divided into two parts, or hemispheres, of east and west longitude.
Y
X
180°W 180°E
What is Longitude?
The earth is divided into 360 equal slices (meridians)
180 west and 180 east of the prime meridian
Y
X
180°W 180°E
What is Latitude?
Our latitude and longitude might be:
40° 54′ 51.09″ N
73° 7′ 28.97″ W
Y
X
90°S
90°N
So Where is (0,0)? The origin point (0,0) is where the equator intersects the prime meridian.
(0,0) is off the western coast of Africa in the Atlantic Ocean.
See If You Can Tell In Which
Quarter These Lon/Lats Are
Located
1. 41°N, 21°E
2. 37°N, 76°W
3. 72°S, 141°W
4. 7°S, 23°W
5. 15°N, 29°E
6. 34°S, 151°E
A B
C D
1. B
2. A
3. C
4. C
5. B
6. D
See if you can find those same
latitude/longitude locations on a
map!
Equator Latitude 0o
Latitude: (90oN to 90oS)
Latitude 23½o North Tropic of Cancer
Latitude 23½o South Tropic of Capricorn
Longitude 30o East
Longitude 60o East
Longitude 30o West
Longitude 60o West
Positioning on the Earth’s Surface
East is the direction of rotation of the Earth North Pole
South Pole
23½o 23½o
66½o 90o
900
21st June
22nd December
22nd Sept
20th March
30oE 60oE 90oE 90oW 30oW 60oW
Longitude 90oEast Longitude 90o West
Prime Meridian
0o Longitude
Longitude: (180oE to 180oW)
Latitude and Longitude together enable the fixing of position on the Earth’s surface.
Now you’re ready to
find some locations on
a map!
Point, line and area mapping
75
Levels of data
Nominal
Qualitative classification into groups
No implicit ordering
Ordinal
Ranked according to relative measures
Numerical distance has no meaning
Constant unit difference defines qualitative rather than quantitative relationships
Interval
Quantitative variable with an arbitrary zero origin
Temperature scales (0° Celsius does not equal 0° Fahrenheit)
Ratio
Quantitative variable with a non-arbitrary zero origin
Includes most of the counting information included on maps
76
Nominal map data
77
78
Nominal data.
Colors represent
different rock types
on the surface of
Mars.
79
Nominal data.
Colors represent
different vegetation
types in Canada
Ordinal map data
Numerical distance has no
meaning. Constant unit difference
defines qualitative rather than
quantitative relationships. For
example, the international airport
may be 10X busier than the
national airport and 100X busier
than the regional airport. You
should not assume that the
international airport is twice as
busy as the national airport, and
three times as busy as the regional
airport. They are ranked in relative
terms, 1st, 2nd, 3rd, but that does
not tell you anything about how
different in magnitude each ordinal
level is. They are just ranked.
80
Ratio map data
81
Types of point pattern maps
Dot density maps using nonproportional point symbols
Does not vary in size
1 dot equals 10,000 people
Dots can be nominally differentiated by varying the shapes or colors of the point
symbols
Proportional circle map
Point data mapped with a circle instead of a dot
Size of circle relates to measured variable and not necessarily the area over which
it is measured
Two types of proportional circle maps
Continuously variable symbols
Range-graded symbols
82 http://www.d.umn.edu/geog/cartfolder/HTML%20Pages/Map-Types.htm
Dot density map
83
84
Dot density map animation
Dot density map using color to classify depth of earthquake events
Proportional circle map (continuously graded).
Continuously graded proportional circles come in all sizes
86
Proportional circle map (continuously graded). Additional
information provided in pie charts.
87
Range-graded proportional circle map. Only a set number of circle sizes are
used (four in this map).
88
Range-graded proportional circle map
89
Proportional circle map (continuously graded) used to convey
density of subscribers to the Chicago Tribune newspaper
Line maps
Flow maps
May show the actual path of entities across a surface and their intensity
Flow maps may also show idealized locations of the travel path. When path is idealized, type of flow map is desire line map. Shows only general direction, not actual path.
Common examples of flow maps, a type of line map
Traffic flow map
Social network map
Exchange of goods and services between locations
92
Telecommunications flow map showing desire lines (actual path
between locations is very different from the idealized routes shown).
Projected average annual truck traffic in Florida, 2020. Path and
intensity is shown in this flow map.
http://ops.fhwa.dot.gov/freight/freight_analysis/state_info/florida/profile_fl.htm
Social network map
Social network map
(note that this map
shows relative space,
not the actual, or
absolute, space in the
real world. Distance in
map is related to family
and friendship ties.
Researchers consider
these flow maps
because information
moves through these
networks. This is also a
statistical map.
Area maps: choropleth maps
Choropleth maps portray areal data. The map below is a choropleth map
Areal divisions are often boundaries like census tracts, counties, states.
96
97
Area maps: choropleth maps
Areal averaging
Numerical values for an areal unit in a choropleth
map may be areally averaged.
Common ways to areally average choropleth map
data
Density (persons per sq mile)
Percentages (all data relativized to a scale of 0-100)
98
99
An areally averaged choropleth map. Population in counties is relativized
to the number of people per square mile.
100
An areally averaged choropleth map. Native American population in
counties is relativized (as a percentage) to the total number of Native
Americans.
Whether or not a map is
areally averaged greatly
alters the patterns
communicated. At top,
an unstandardized
choropleth map. It is not
areally averaged in any
way.
This is a standardized,
areally averaged
choropleth map. Note
that the patterns are
very different. Which
map should you use?
101
Areal pattern analysis Geographers also examine how patterns can change depending upon the size and shape of an areal unit. What if we
could pick and choose counties to combine? What if we color coded the popular term used by state? How would the
map change? The way values for areal units changes depending upon where boundaries are located is called the
modifiable areal unit problem.
102
The modifiable areal unit problem
103
Its easy to manipulate choropleth
maps, for better and for worse
These practices can change the way patterns are presented in a choropleth map:
Whether or not the map is areally averaged.
How the modifiable areal problem is expressed---how the areal units are chosen
Choice of choropleth classification technique (Equal steps? Quantile? Natural breaks? Minimum variance? Natural breaks and minimum variance are more objective)
104
Practice:
Data level?
Map types?
105
Data levels? Map types?
106
River characteristics as observed by Lewis and Clark (1804-1805).
The area of the circle is proportional to the channel width. The color
of the large circle approximates the color of the water (gray indicates
no color was mentioned in the journals). Descriptions of the bed
material are determined by the position of the solid black circle within
the black triangle. The example in the upper right indicates a width of
500 yards, a yellow water color, and bed material that is mostly sand
with some gravel and some mud. (http://pubs.usgs.gov/fs/fs-004-03/)
Data level? Map types?
107