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Chapter 1

# GEOG 102 Chapter Notes - Chapter 1: Spheroid, Mercator Projection, Map Projection

Department
Geography
Course Code
GEOG 102
Professor
Ellsworth Le Drew
Chapter
1

Page:
of 3
GEOG102 // Visualizing Physical Geography
The Earth as a Rotating Planet
The Shape of the Earth (p.4-5)
oEarth slightly bulges at the equator and flattens at the pole
Equatorial diameter = 12,756km
Polar diameter = 12,714km
Shape is more like a oblate ellipsoid rather than a sphere
More accurate representation would be a geoid
Bulge caused by the Earth's rotation
The Earth's Rotation (p.6-7)
oThe Earth spins on its axis
Axis - imaginary straight line through center of the Earth around which the
earth rotates
oEarth spins counter-clockwise at the North Pole
Left to Right from Equator
One rotation is one solar day (24 hours)
oNorth and South poles are two points on the Earth's surface where axis of rotation
emerges
oCoriolis effect - directions of large motions of the atmosphere and oceans are
affected as the turning planet makes their paths curve
The Geographic Grid (p.8-12)
oNetwork of parallels and meridians used to fix location on the Earth
Parallel - East-west circle on the Earth's surface, lying on a plane parallel to
the equator
Meridian - North-south line n the Earth's surface, connecting the poles
oParallels and Meridians
Earth is divided into a geographic grid which is a network of parallels and
meridians
Geographic grid - network of parallels and meridians used to fix
location on the Earth
Parallel - East-west circle on the Earth's surface, lying in a plane
parallel to the equator
Meridian - North-south line on the Earth's surface, connecting the
poles
oLatitude and Longitude
Longest parallel of latitude is the equator which lies midways between two
poles
Latitude - Arc of a meridian between the equator and a given point on
the globe
Longitude - Arc of a parallel between the prime meridian and a given
point on the globe
Equator - Parallel of latitude lying midway between the Earth's poles
(0°)
Together, latitude and longitude pinpoint locations on the geographic grid
Map Projections (p.13-15)
oMap Projections - A system of parallels and meridians representing the Earth's
curved surface drawn on a flat surface
oMercator Projection
Map projection with horizontal parallels and verticals meridians
Form a rectangular grid of vertical and horizontal straight lines
At higher latitudes the spacing between lines increase
GEOG102 // Visualizing Physical Geography
Goal of the Mercator Projection was to create a map that sailors use to
determine their course
However, Mercator's map can easily make the shortest distance between two
points seem longer than the compass line joining them
Chosen for maps of temperatures, winds, and pressures
oThe Goode Projection
Indicates the true sizes of regions on the Earth's surface
Ideal for showing the world's climate, soils, and vegetation
oPolar Projection
Centered on the North or the South Pole
Essential for weather maps of the polar regions
Equator forms the outer edge of the map
Global Time (p.18-23)
oEarth's geographic grid and rotation helps define global time
oStandard Time
Standard Time - Time system based on the local time of the standard
meridian and applied to belts of longitude extending roughly 7 1/2° on either side
of the meridian
Time zones - Zones or belts within which standard time applies
oWorld Time Zones
Country with greatest number of time zones = Russia
China covers five but runs on a single national time using the standard
meridian of Beijing
oInternational Date Line
Greenwich = 0° meridian
180th meridian servers as the international date line
oDaylight Saving Time
Allows us to transfer an hour of light to a more useful time
The Earth's Revolution Around The Sun (p.24-28)
oThe Earth takes 365.242 days to travel around the sun
Approximately a quarter of a day longer than the calendar day of 365 days,
thus every four years there is a 366th day
oPoint where the Earth is closest to the sun = Perihelion (around Jan. 3)
oPoint where the Earth is farthest away = Aphelion (around July 4)
oElliptical orbit is still very close to a circle so the difference is around 3%
oThe Moon is permanently facing the Earth on one side due to the
synchronization of the rate that it rotates around the Earth and for it to
rotate on its axis
oTilt of the Earth's Axis
Seasons exist because the Earth is not perpendicular to the plane
containing the Earth's orbit (plane of the ecliptic)
The North Pole always points towards Polaris (North Star)
oThe Four Seasons
Winter Solstice (Dec.21-22) = North polar end of the Earth leans at the
maximum angle (23 1/2°)away from the sun
Summer Solstice (June 21 - 22) = North polar end points at the sun at the
maximum angle
Equinox (Mar. 21 - vernal, Sept. 23 - autumnal) = instant in time when the
sub solar point falls on the Earth's equator and the circle of illumination passes
through both poles
oEquinox Conditions
Day and Night are equal length everywhere around the globe
GEOG102 // Visualizing Physical Geography
Subsolar point is the point here the sun is directly overhead at a particular
moment
At Equinox the circle of illumination passes through both North and South
poles
Therefore surface of the poles receive very little solar energy
Equator receives a lot of solar energy
oSolstice Conditions
During Summer Solstice the day is longer (about 15 hours)
North of lat. 66 1/2° N the day is unbroken for 24 hours
During Winter Solstice the night is longer (about 15 hours)
North of lat. 66 1/2° N the night is unbroken for 24 hours