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GIS > Chapter 2 > Flashcards

Chapter 2 Flashcards

1
Q

what is weird about the mercator projection

A

it distorts the size of the countries

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2
Q

on the mercator map what is bigger Greenland or Canada, and is that accurate?

A

Mercator shows Greenland is bigger but in reality Canada is much bigger

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3
Q

what is Geodesy

A

the study of the earth’s shape, orientation in space and gravity

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4
Q

what is the general shape of the earth

A

an ellipsoid

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5
Q

is the earth a perfect sphere

A

NO

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6
Q

where does the earth bulge

A

at the equator

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7
Q

what is a geoid

A

a model of earth using sea level as a base

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8
Q

what causes variations in strength of gravity’s pull

A

variations in size, shape and mass of earth

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9
Q

what region on earth has stronger gravitational pull

A

mountains (regions with more mass)

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10
Q

what region on earth has weaker gravitational pull

A

areas with less mass (valleys)

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11
Q

what is the geoid of earth based on

A

the idea that water covers the entire surface of earth and it is not affected by moon, wind or waves

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12
Q

what does a geoid measure

A

global mean sea level that is used to measure precise surface elevations

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13
Q

what force ONLY affects a geoid

A

gravity

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14
Q

what does a geoid define

A

zero elevation (elevation around earth is generally the same)

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15
Q

describe where the geoid of earth rises and falls

A

rising where gravity is high

sinking where gravity is low

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16
Q

what is a datum

A

a reference surface/model of earth

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17
Q

what is a datum used for

A

plotting locations

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18
Q

what shape is a datum

A

ellipsoid

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19
Q

where is a datum in respect to the geoid

A

above in some spots and below in others

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20
Q

describe two types of datums

A

local datums approximate the Earth’s shape in a specific area

global datums approximate the Earth’s shape globally

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21
Q

what are two examples of datums

A

World Geodetic System 1984 (WDS84)

North American Datum 1983 (NAD83)

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22
Q

is WGS84 a global or local datum

A

global (designed to model the whole earth)

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23
Q

is NAD83 a global or local datum

A

local - designed to model NA only

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24
Q

what is datum transformation

A

a series of calculations that change one datum to another

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25
Q

where on the earth is there flattening

A

at the poles

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26
Q

where on earth is there bulging

A

at the equator

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27
Q

what does the geoid model use to determine mean sea level

A

differential forces in gravity

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28
Q

what are used to establish geographic coordinate systems (GCS)

A

datums

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29
Q

what are geographic coordinate systems (GCS)

A

global reference system for determining a location on a 3D ellipsoid

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30
Q

what type of units are used in GCS

A

angular units

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31
Q

what are used for finding location with GCS

A

lines of longitude and latitude

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32
Q

what is longitude

A

imaginary lines on the globe that run from pole to pole

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33
Q

what is the origin (0 degrees) for longitude

A

prime meridian

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34
Q

what are longitude measurements east of the prime meridian

A

positive

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35
Q

what are longitude measurements west of the prime meridian

A

negative

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36
Q

what direction do longitudinal values increase

A

moving east and west

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37
Q

what is the max degrees for longitude

A

180 east and west

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38
Q

where do lines of longitude meet

A

center of the pacific ocean (180 degrees)

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39
Q

is this longitude or latitude

A

longitude

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40
Q

what is latitude

A

imaginary lines on the globe running east to west

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41
Q

where is the origin for latitude

A

the equator

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42
Q

what are latitude measurements north of the equator

A

positive

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43
Q

what are latitude measurements south of the equator

A

negative

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44
Q

is this longitude or latitude

A

latitude

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45
Q

what is the max degrees for latitude

A

90 north and south

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46
Q

what is the north quadrant of the globe

A

all positive latitudes north of equator

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47
Q

what is the South quadrant of the globe

A

all negative latitudes south of equator

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48
Q

what is the east quadrant of the globe

A

all positive longitudes EAST of prime meridian

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49
Q

what is the west quadrant of the globe

A

all negative longitudes west of prime meridian

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50
Q

how many minutes are in a degree

A

60

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51
Q

how many seconds are in a degree

A

3600

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52
Q

what fraction of a circle is 1 degree

A

1/360 of a circle

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53
Q

1 minutes is how many degrees

A

1/60 of a degree

54
Q

what are the axes when plotting longitude and latitude on a cartesian plane

A

x axis - longitude

y axis - latitude

55
Q

what does DD stand for

A

decimal degree

56
Q

what is DD

A

the fractional decimal equivalent to DMS

57
Q

what is DMS

A

degrees minutes second

58
Q

what does a negative sign mean in DMS

A

locations that are south or west

59
Q

how to convert DMS to DD

A

DD = D + (M/60) + (S/3600)

60
Q

what is a problem when rounding decimals in coordinate systems

A

can drastically change where you end up in the world

61
Q

why is measuring distance in GCS a problem

A

because lines of latitude are equally spaced across the world but longitude is NOT

62
Q

what is key to all geographical applications

A

spatial location

63
Q

what are map projections

A

conversion of location from a 3D earth to a 2D surface

64
Q

what is the issue with projections

A

the distortion that results (distortion of size, shape, distance or direction)

65
Q

what must you project onto when doing projections

A

a developable surface

66
Q

what is a developable surface in projections

A

a piece of paper wrapped around the globe

67
Q

three main types of developable surfaces

A
  1. azimuthal
  2. conical
  3. cylindrical
68
Q

contrast the three types of developable surfaces

A
  1. azimuthal
    the surface touches the globe in ONE spot
  2. conical
    the surface covers the globe in a cone like shape
  3. cylindrical
    the surface wraps around the earth like a cylinder
69
Q

type of developmental surface

A

conical

70
Q

type of developmental surface

A

cylindrical

71
Q

type of developmental surface

A

azimuthal

72
Q

what are three ways of orientating the developmental surface

A
  1. normal
    - wraps around the equator
  2. transverse
    - wraps around longitude
  3. oblique
    - wraps around on an angle
73
Q

conical vs secant projection types

A

conical
- touches the globe at a single point

secant
- cone projection touching it along two latitude lines

74
Q

what is the lambert conformal conic project

A

a conical secant projection that minimizes distortion and maintains local angles and shapes

75
Q

type of projection

A

lambert conformal conic project

76
Q

what type of projection isthe mercator projection

A

a cylindrical projection

77
Q

what does the mercator projection distort

A

size of countries
(poles are larger and equator is smaller)

78
Q

what was the mercator projection used for

A

navigation by compass

79
Q

type of projection

A

mercator projection

80
Q

what does the peter’s projection distort

A

elongates size of continents at the equator and compresses them at the poles

81
Q

type of projection

A

peter’s projection

82
Q

what are some potential reasons maps have north at the top

A
  1. sailors used compasses and north star to navigate
  2. mercators map orients north in 1569 and sets the trend
  3. north is up based on Europeans doing most of exploring
83
Q

is most of world’s pop in north or south hemisphere

A

north

84
Q

is Africa in north or south hemisphere

A

most is in the north

85
Q

what makes up the majority of southern hemisphere

A

water

86
Q

how much of earth’s land is in the southern hemisphere

A

33%

87
Q

are there maps that are right

A

NO - all are wrong in some way

88
Q

are projected maps correct

A

NO - impossible to accurately transcribe 3D object on 2D surface

89
Q

what is the projected coordinate system

A

coordinates on a flat 2D surface

90
Q

what are constant in the projected coordinate system

A
  1. lengths
  2. angles
  3. areas
91
Q

what is the projected coordinate system based on

A

geographic coordinate system (GCS)

92
Q

what is the most common type of projected coordinate system

A

universal transverse mercator (UTM)

93
Q

what does the UTM do

A

divides earth into 60 zones that are EACH 6 degrees in longitude

94
Q

what latitudes does the UTM NOT exceed

A

84 degrees NORTH
80 degrees SOUTH

95
Q

where does the UTM start counting and in what direction

A

counts east from the 180th meridian

96
Q

how are zones in the UTM split

A

north and south of the equator

97
Q

what zone is alberta in

A

zone 11 and 12

98
Q

what does each zone in the UTM have

A

x and y coordinates measured in meters

99
Q

describe what the x and y coordinates mean in a UTM zone

A

the x coordinate counts east or west of the central meridian

the y coordinate counts north or south from the equator

100
Q

what is easting and northing in UTM zones

A

northing refers to the y coordinate of a zone

easting refers to a x coordinate of a zone

101
Q

in the UTM where does northing count in the northern hemisphere

A

from the equator (and up)

102
Q

what does the equator have a value of in the North hemisphere

A

0

103
Q

what does the equator have a value of in the southern hemisphere

A

10 million

104
Q

how is a location found in the southern hemisphere using UTM

A

subtracting the distance from the false northing

105
Q

what does a false northing refer to

A

in the UTM a false origin of 10,000,000 meters south of the equator is used to avoid negative northings

106
Q

what is easting in the UTM

A

distance east or west of the central meridian

107
Q

what is false easting in UTM

A
108
Q

contrast false easting from northing

A

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

109
Q

what coordinate (x or y) does false easting affect

A

x coordinate

110
Q

what coordinate (x or y) does false northing affect

A

y coordinate

111
Q

why does the UTM have false easting and northing

A

to ensure x and y values are always positive

112
Q

are locations EAST of the central meridian added or subtracted

A

added

113
Q

are locations WEST of the central meridian added or subtracted

A

subtracted

114
Q

why do UTM locations need a zone number attached to the coordinates

A

because easting and northing values repeat in each of the 60 zones

115
Q

pros of UTM

A
  1. minimal distortion
  2. uniform grid system (used all over world)
  3. global coverage
116
Q

cons of UTM

A
  1. cannot be used in polar regions
  2. limited width zones (each zone stuck in the 6 degrees longitude)
117
Q

what are two special UTMs built for AB

A
  1. 10 TM
    expands the 6 degree width of each zone to 10 degrees
  2. 3TM
    decreases the 6 degree zones to 3 degrees
118
Q

what was western canada divided into

A

7 one square mile sections

119
Q

what were the 7 sections of Western Canada defined by

A

meridians

120
Q

what are the 7 meridian systems going from East to West in Canada

A
  1. west of Winnipeg
  2. Manitoba/sask border
  3. moose jaw sask
  4. sask/AB border
  5. Calgary
  6. grand prairie
121
Q

what is the base unit for the dominion land survey

A

township

122
Q

what is a township

A

6 mile x 6 mile area of land

123
Q

how many tires of townships are there in the dominion land survey

A

two tiers to the north AND two tiers to the south

124
Q

where in a township is it smaller? larger?

A

north - smaller

south - larger

125
Q

how are townships designated

A

township number and range number

126
Q

what is township 1

A

the FIRST north of the First baseline (canada/US border)

127
Q

how do township numbers increase from township 1

A

northward

128
Q

what happens when range numbers meet at each meridian

A

they restart counting from range 1 INCREASING to the WEST

129
Q

describe how townships are further broken down

A

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

130
Q
A

GIS (5 decks)

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