GOALS OF THIS CHAPTER
Define Geography and Physical Geography
Geography as an Earth Systems Science
An Introduction to Systems Thinking
Earth’s Reference Grid
Basics of Cartography: Map Scale and Projection
GEOGRAPHY
Geo (“Earth”) + Graphein (“to write”)
Geography is the study of synergistic interactions
among natural systems, geographic areas, society,
and cultural activities over space
Spatial analysis is the key to geography
•The nature and character of physical space
•The influence of space on Earth system processes
Geography – a diverse discipline including elements of the
following interrelated physical and human disciplines (Fig 1-2)
PHYSICAL
Cartography
Pedology
Meteorology
Chemistry
Remote Sensing
Biogeochemistry
Environmental Modelling
HUMAN
Geomorphology
Geology
Biology
Physics
Geographic Information Systems
Biogeography
History
Sociology
Land Use Planning
Population Studies
Cultural Studies
Political Science
Medical Geography
Sound disorganized ?
Discipline held together by spatial analysis.
Human and physical geographers often work together
Humans are part of nature and, thus, affect and are affected
by, the physical environment.
What is Physical Geography ?
“The spatial analysis of all the physical elements
and processes that make up the environment:
energy, air, water, weather, climate, landforms,
soils, animals, vegetation and Earth itself.”
Physical Geography is an Earth Systems science
As a science, it employs the scientific method(Fig 1)
The main concept of Earth Systems science is that:
“interacting physical, chemical and biological
systems produce the conditions of the whole Earth.”
A Brief Introduction to Systems Thinking
System – defined
(Fig 1-3, 1-5, 1-6)
“(An) interrelated set of (components) and their
attributes, linked by flows of energy and matter, as
distinct from the surrounding environment”
•Energy can be transformed
•A system may be open or closed
Most natural systems are open
(energy flows in and out)
Earth’s Four Spheres
(Fig 1-7)
Atmosphere
Thin, gaseous veil surrounding the Earth, held together by the
force of gravity. Nitrogen, oxygen, argon, carbon dioxide, water
vapour and trace gases.
Hydrosphere
The Earth’s waters on the surface, within the uppermost portion of
The crust and in the atmosphere.
Lithosphere
The solid planet (soil, crust and a portion of the upper mantle)
Biosphere
The area in which physical and chemical factors form the context of
life
Sample systems:
•The carbon cycle (clearly human and physical)
•An ecosystem
•The water cycle (global, regional, catchment)
Emerging Field in Earth Systems Science and
Physical Geography: Environmental Modelling
(spatial and temporal simulation Earth’s systems)
Example: A leaf (Figure 1-4)
Two subsystems determine net carbon uptake
Photosynthesis
Inputs: sunlight, water, nutrients, carbon dioxide
Inputs converted to stored chemical energy (carbohydrates)
Outputs: oxygen
Respiration
Carbohydrates converted to carbon dioxide, water and heat
Systems Example
Modelling in Physical Geography
and the Earth Sciences
Systems
All Systems are composed of the following
four elements:
1.
2.
3.
4.
Reservoirs
Processes
Converters
Interrelationships
Reservoir:
A repository where something is accumulated,
stored and sometimes passed on to other elements
in the system.
Reservoirs may accumulate or diminish over time
Examples:
Total mass of carbon storage in biomass in
a global carbon cycle model
Number of specimens of a species in a
predator/prey model
Process:
An ongoing activity in a system that determines
the content of a reservoir over time
Future contents =
previous contents
+ all inflows
- all outflows
R(t+t) = R(t) + {sum of inflows - sum of outflows}
Snowmass water equiv alent
Addition
PROCESS
RESERVOIR
(water equivalent precipitation as
snow, ice pellets or freezing rain
in one day)
Remov al
PROCESS
(water-equivalent removal through
melting, evaporation and
sublimation and infiltration
in one day)
Converters:
System variables that can play different roles
within the system
-
Regulate the rates at which processes within
the system operate
Freezing rain
Melting
Ice pellets
Sublimation
Snow
Snowmass water equiv alent
Addition
Remov al
Interrelationships between
Reservoirs, Processes and
Converters
Solar radiation
Windspeed
Rainf all
Melting
Freezing rain
Temperature
Humidity
Ice pellets
Sublimation
Snowmass water equiv alent
Snow age
Remov al
Additions
Snow
Snow density
Snowdepth Modelling:
Conceptual Model
Snow depth
What is the point in thinking in terms of systems?
Uses of System Models:
1.
To understand the complex mechanisms
controlling system function
-
Describe processes and converters
-
Identify mechanisms behind observed
cycles and complex patterns that cannot
be intuitively induced based on the simple
relationships between two variables
-
Determine how the system maintains
stability and how that stability can be
jeopardized
2.
“Predict” and “Validate” System Performance
-
Project cycles and trends
-
Evaluate impact of policy options and
scenarios (eg. impact of greenhouse gas
emission scenarios on global warming and
carbon cycling)
-
Identify scenarios that may jeopardize or
restore system stability
Feedback Loops:
A closed-loop circle of cause and effect in which
“conditions” in one part of the system cause “results”
which, in turn, alter the “original” conditions
Positive feedback :
Changes at one point of a feedback loop eventually
amplify or reinforce the original change
-
Such systems tend to lose control
-
Example:
Positive feedback to anthropogenically-induced
global warming via wetlands (arguably)
Negative Feedback:
Changes at one point of a feedback loop eventually
counteract (damp out) the original change
-
Such systems tend to be self-regulating and do not
run out of control
-
Many environmental problems can be attributed to a
breakdown of naturally-occurring negative feedback
loops
Example:
High birth rate in a given species leads to
higher population, which reduces resources.
Higher death rates and reduced birth rates result,
leading to a reduction in the population and an increase
in resource availability.
Steady-state Equilibrium:
Systems which “level off,” so that the system
reservoirs change little with time are said to have
reached steady state
Inputs of energy/matter equal outputs
Storage is constant
Dynamic System Behaviour:
1.
Linear growth or decay
R(t) = a + bt ,
where a is the value of R(t) at t=0 and
b is the rate of change
2.
Exponential growth or decay
R(t) = R0ekt,
where k is the net growth rate (positive) or
decay rate (negative) of R(t)
3.
Overshoot and collapse
4.
Logistic growth
5.
Oscillation
Basic Principles of Cartography
The Spherical Earth
Incan astronomers accurately calculated the precession of the
equinoxes – did they understand the Earth was spherical ?
Ancient Greece: Pythagoras (2503-2583 BP)
Aristotle proved Earth to be spherical in (2387-2325 BP)
Ancient Egypt:
Eratosthenes calculated the polar circumference (2250 BP)
England:
Newton predicted that Earth bulges slightly at equator (316 BP)
Today: Geodesy - Earth’s shape and size characterized by
surveys and mathematical calculations – Geoid
Latitude and Longitude
Ptolemy - Divided Earth into 360, 60, 60 system (1838-1918 BP)
Latitude
“An angular distance north or south of the equator, measured
from the centre of the Earth”
Parallel
“a line connecting all points along the same latitudinal angle”
(eg. Arctic/Antarctic Circle, Equator, Tropic of Cancer/Capricorn)
Longitude
“An angular distance east or west of a point on the Earth’s
surface, measured from the centre of the Earth”
Meridian
“a line connecting all points along the same longitude”
(eg. The arbitrary prime meridian running through Greenwich)
Today: Global Positioning Systems (GPS)
latitude on an ellipsoid approximating the shape o
How
can
latitude
and
longitude
the Earth, but how can the ellipsoid be represented
be
represented
in
2D
?
in two dimensions for GIS images or maps ?
Since maps are constructed in 2D, rather than on ellipsoidal
geometry, projections are required (conical, azimuthal or
cylindrical depending on specific needs of end-user)
Map projections
Two-dimensional representations of the Earth’s surface or
part of the Earth’s surface
Distortions of conformality, distance, direction, scale,
and area ALWAYS result from this process.
Some projections minimize distortions in some of these
properties at the expense of maximizing errors in others.
Other projections only moderately distort all of these
properties.
Conformality
•Scale is the same in any direction at a given point
•Meridians (lines of longitude) and parallels (lines of
latitude) intersect at right angles.
•Shape is preserved locally
Equidistance
Two identical lines from the centre of the projection cover
the same true length in any direction
Preservation of Direction
Azimuths (angles from a point on a line to another point)
are portrayed correctly in all directions
Equal Area
Areas in different regions of the map have the same
proportional relationship to the same areas on the Earth’s
surface
Projection Types: (Fig. 1-18)
1.
2.
3.
4.
Cylindrical
Conical
Azimuthal
Oval
Cylindrical Projections
Spherical surface projected
onto a cylinder
Cylindrical
Projection
Surface
Cylindrical Equal-Area projections
Straight meridians and parallels
Meridians are equally spaced, parallels unequally spaced
There are normal, transverse, and oblique cylindrical equal-area
projections.
Scale is true along the central line (equator for normal, central
meridian for transverse, selected line for oblique) and along any
two lines equidistant from the central line.
Shape and scale distortions increase with distance from central
line
Useful for navigation:
All straight lines are lines of
constant azimuth.
Universal Transverse Mercator [UTM]
World divided into 60 zones
Zones numbered eastward from 1 to 60 beginning at 180 degrees west.
The central meridian of each zone is given an easting of 500,000 m.
For the northern hemisphere, the equator has a northing of 0 m.
For the southern hemisphere, the equator has a northing of 10,000,000 m.
Scale distortion within a UTM zone ranges from .9996 to 1.0003.
A standard for many countries
Commonly used in topographic mapping and for referencing satellite imagery.
System of UTM and UPS (Polar) grid zone designations
Quadrilaterals are defined by column number and row letter
(I and O are omitted). The darkened area is quadrilateral 32N.
UTM designed to function between 80 S
and 84 N. Covers all of Canada
To keep distortion to a minimum surface
of globe projected down to a surface
using 60 N-S strips, each 6 degrees wide.
UTM grid then placed over each zone
The Mercator projection is conformal. In
other words, corrected compass bearings
are straight lines.
Conical Projections
Conic projections result
from projecting a spherical
surface onto a cone.
Conical
Projection Surface
Polyconic Projection: Central Median 100ºW
Conical Projections
Example:
Albers Equal Area Conic, Origin 23N, 96W
Distorts scale and distance except along standard parallels.
Areas proportional and directions true in limited areas.
Used in large countries with a greater E-W than N-S extent.
Azimuthal Projections
Azimuthal projections result
from projecting a spherical
surface onto a plane.
Used to show air-route distances.
Distances measured from
centre are true.
Distortion of other properties
increases away from
the center point.
Example:
Azimuthal Equidistant
Projection
Two Different Projections of North America
The use of an appropriate
projection system is
dependent on the purpose
and location of the region
studied
Cartesian Coordinate
System (X,Y)
Define an origin
Define a positive X direction
Define a positive Y direction
orthogonal to X
Define linear displacement from the
origin in X and Y
Euclidian Distance:
Distance, D, between two points
(X1, Y1) and (X2, Y2) can be
calculated as follows:
Maps, scales and projections
The ratio of the image on a map to the real world is called scale
For example, a scale of 1:25,000 means that 1 unit on the map
represents 25,000 units on the ground.
Map scales:
Written scale (eg. 1:25,000)
Representative fraction (eg. 1/25,000)
Graphic scale - Scale remains true after enlarged/reduced
The greater the denominator, the smaller the scale
In other words, a large scale map (eg. 1:10,000) shows more detail
and less area than a small scale map (eg. 1:1,000,000).
Map Scale
Calculating map scale:
You have scanned a portion of a map for which the scale is known
and enlarged it. How can you determine the scale of your new map ?
1.
Find a similar object on each map (eg. line segment) and measure
the distance on each map.
2.
Let’s say the reference map has a scale of 1:24 000 and you
measured a line segment distance of 65 mm. Multiply the
measurement by the denominator of the scale fraction
(65 x 24 000 = 1 560 000). Now you have the distance on the
Earth’s surface.
3.
Divide this distance by the measurement on your new map
(eg. 80 mm). Your scale is 1 560 000/ 80 or 1: 19500
Is this a larger scale or smaller scale ?
(Larger, just like your measurement)
More mapping basics: Contour Lines
A method of depicting 3dimensional character of
the terrain on a 2dimensional map.
Sample Topographic Map
*NB: The U of L Library has a
large collection of 1:50,000 and
1:250,000 maps produced
by the Canada Centre for
Mapping (Natural Resources
Canada)
http://imnh.isu.edu/digitalatlas/geog/basics/topo.htm
Can you infer general wind direction and
relative windspeed from this map ?
A tight
pressure
gradient
leads to
higher wind
speeds
Winds blow clockwise around H pressure, counter clockwise into L pressure