Chapter 2 Flashcards
what is weird about the mercator projection
it distorts the size of the countries
on the mercator map what is bigger Greenland or Canada, and is that accurate?
Mercator shows Greenland is bigger but in reality Canada is much bigger
what is Geodesy
the study of the earth’s shape, orientation in space and gravity
what is the general shape of the earth
an ellipsoid
is the earth a perfect sphere
NO
where does the earth bulge
at the equator
what is a geoid
a model of earth using sea level as a base
what causes variations in strength of gravity’s pull
variations in size, shape and mass of earth
what region on earth has stronger gravitational pull
mountains (regions with more mass)
what region on earth has weaker gravitational pull
areas with less mass (valleys)
what is the geoid of earth based on
the idea that water covers the entire surface of earth and it is not affected by moon, wind or waves
what does a geoid measure
global mean sea level that is used to measure precise surface elevations
what force ONLY affects a geoid
gravity
what does a geoid define
zero elevation (elevation around earth is generally the same)
describe where the geoid of earth rises and falls
rising where gravity is high
sinking where gravity is low
what is a datum
a reference surface/model of earth
what is a datum used for
plotting locations
what shape is a datum
ellipsoid
where is a datum in respect to the geoid
above in some spots and below in others
describe two types of datums
local datums approximate the Earth’s shape in a specific area
global datums approximate the Earth’s shape globally
what are two examples of datums
World Geodetic System 1984 (WDS84)
North American Datum 1983 (NAD83)
is WGS84 a global or local datum
global (designed to model the whole earth)
is NAD83 a global or local datum
local - designed to model NA only
what is datum transformation
a series of calculations that change one datum to another
where on the earth is there flattening
at the poles
where on earth is there bulging
at the equator
what does the geoid model use to determine mean sea level
differential forces in gravity
what are used to establish geographic coordinate systems (GCS)
datums
what are geographic coordinate systems (GCS)
global reference system for determining a location on a 3D ellipsoid
what type of units are used in GCS
angular units
what are used for finding location with GCS
lines of longitude and latitude
what is longitude
imaginary lines on the globe that run from pole to pole
what is the origin (0 degrees) for longitude
prime meridian
what are longitude measurements east of the prime meridian
positive
what are longitude measurements west of the prime meridian
negative
what direction do longitudinal values increase
moving east and west
what is the max degrees for longitude
180 east and west
where do lines of longitude meet
center of the pacific ocean (180 degrees)
is this longitude or latitude
longitude
what is latitude
imaginary lines on the globe running east to west
where is the origin for latitude
the equator
what are latitude measurements north of the equator
positive
what are latitude measurements south of the equator
negative
is this longitude or latitude
latitude
what is the max degrees for latitude
90 north and south
what is the north quadrant of the globe
all positive latitudes north of equator
what is the South quadrant of the globe
all negative latitudes south of equator
what is the east quadrant of the globe
all positive longitudes EAST of prime meridian
what is the west quadrant of the globe
all negative longitudes west of prime meridian
how many minutes are in a degree
60
how many seconds are in a degree
3600
what fraction of a circle is 1 degree
1/360 of a circle
1 minutes is how many degrees
1/60 of a degree
what are the axes when plotting longitude and latitude on a cartesian plane
x axis - longitude
y axis - latitude
what does DD stand for
decimal degree
what is DD
the fractional decimal equivalent to DMS
what is DMS
degrees minutes second
what does a negative sign mean in DMS
locations that are south or west
how to convert DMS to DD
DD = D + (M/60) + (S/3600)
what is a problem when rounding decimals in coordinate systems
can drastically change where you end up in the world
why is measuring distance in GCS a problem
because lines of latitude are equally spaced across the world but longitude is NOT
what is key to all geographical applications
spatial location
what are map projections
conversion of location from a 3D earth to a 2D surface
what is the issue with projections
the distortion that results (distortion of size, shape, distance or direction)
what must you project onto when doing projections
a developable surface
what is a developable surface in projections
a piece of paper wrapped around the globe
three main types of developable surfaces
- azimuthal
- conical
- cylindrical
contrast the three types of developable surfaces
- azimuthal
the surface touches the globe in ONE spot - conical
the surface covers the globe in a cone like shape - cylindrical
the surface wraps around the earth like a cylinder
type of developmental surface
conical
type of developmental surface
cylindrical
type of developmental surface
azimuthal
what are three ways of orientating the developmental surface
- normal
- wraps around the equator - transverse
- wraps around longitude - oblique
- wraps around on an angle
conical vs secant projection types
conical
- touches the globe at a single point
secant
- cone projection touching it along two latitude lines
what is the lambert conformal conic project
a conical secant projection that minimizes distortion and maintains local angles and shapes
type of projection
lambert conformal conic project
what type of projection isthe mercator projection
a cylindrical projection
what does the mercator projection distort
size of countries
(poles are larger and equator is smaller)
what was the mercator projection used for
navigation by compass
type of projection
mercator projection
what does the peter’s projection distort
elongates size of continents at the equator and compresses them at the poles
type of projection
peter’s projection
what are some potential reasons maps have north at the top
- sailors used compasses and north star to navigate
- mercators map orients north in 1569 and sets the trend
- north is up based on Europeans doing most of exploring
is most of world’s pop in north or south hemisphere
north
is Africa in north or south hemisphere
most is in the north
what makes up the majority of southern hemisphere
water
how much of earth’s land is in the southern hemisphere
33%
are there maps that are right
NO - all are wrong in some way
are projected maps correct
NO - impossible to accurately transcribe 3D object on 2D surface
what is the projected coordinate system
coordinates on a flat 2D surface
what are constant in the projected coordinate system
- lengths
- angles
- areas
what is the projected coordinate system based on
geographic coordinate system (GCS)
what is the most common type of projected coordinate system
universal transverse mercator (UTM)
what does the UTM do
divides earth into 60 zones that are EACH 6 degrees in longitude
what latitudes does the UTM NOT exceed
84 degrees NORTH
80 degrees SOUTH
where does the UTM start counting and in what direction
counts east from the 180th meridian
how are zones in the UTM split
north and south of the equator
what zone is alberta in
zone 11 and 12
what does each zone in the UTM have
x and y coordinates measured in meters
describe what the x and y coordinates mean in a UTM zone
the x coordinate counts east or west of the central meridian
the y coordinate counts north or south from the equator
what is easting and northing in UTM zones
northing refers to the y coordinate of a zone
easting refers to a x coordinate of a zone
in the UTM where does northing count in the northern hemisphere
from the equator (and up)
what does the equator have a value of in the North hemisphere
0
what does the equator have a value of in the southern hemisphere
10 million
how is a location found in the southern hemisphere using UTM
subtracting the distance from the false northing
what does a false northing refer to
in the UTM a false origin of 10,000,000 meters south of the equator is used to avoid negative northings
what is easting in the UTM
distance east or west of the central meridian
what is false easting in UTM
contrast false easting from northing
false northing
- a false origin of 10,000,000 meters SOUTH of the equator is used to avoid negative northings
false easting
- The central meridian is assigned a false easting of 500,000 meters
what coordinate (x or y) does false easting affect
x coordinate
what coordinate (x or y) does false northing affect
y coordinate
why does the UTM have false easting and northing
to ensure x and y values are always positive
are locations EAST of the central meridian added or subtracted
added
are locations WEST of the central meridian added or subtracted
subtracted
why do UTM locations need a zone number attached to the coordinates
because easting and northing values repeat in each of the 60 zones
pros of UTM
- minimal distortion
- uniform grid system (used all over world)
- global coverage
cons of UTM
- cannot be used in polar regions
- limited width zones (each zone stuck in the 6 degrees longitude)
what are two special UTMs built for AB
- 10 TM
expands the 6 degree width of each zone to 10 degrees - 3TM
decreases the 6 degree zones to 3 degrees
what was western canada divided into
7 one square mile sections
what were the 7 sections of Western Canada defined by
meridians
what are the 7 meridian systems going from East to West in Canada
- west of Winnipeg
- Manitoba/sask border
- moose jaw sask
- sask/AB border
- Calgary
- grand prairie
what is the base unit for the dominion land survey
township
what is a township
6 mile x 6 mile area of land
how many tires of townships are there in the dominion land survey
two tiers to the north AND two tiers to the south
where in a township is it smaller? larger?
north - smaller
south - larger
how are townships designated
township number and range number
what is township 1
the FIRST north of the First baseline (canada/US border)
how do township numbers increase from township 1
northward
what happens when range numbers meet at each meridian
they restart counting from range 1 INCREASING to the WEST
describe how townships are further broken down
one township has 36 sections (1 x 1 mile)
EACH of the sections (1 x1 mile) has 4 quadrants
each of the 4 quarter sections are sectioned into 16 legal subdivisions
