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Cartography > Projections and Graticules > Flashcards

Projections and Graticules Flashcards

1
Q

Latitude

A

The angular distance north or south of the equator
A measure of distance, not a place

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2
Q

Great Circle

A

A plane that cuts the Earth in half
Equator
Infinite number as long as the go thru the center (all lines of longitude)

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3
Q

Small Circle

A

A plane through the Earth but not in half

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4
Q

Parallel

A

Specific small circles parallel to the equator
Parallels are NOT latitudes
A specific “place” not a distance
Infinite number of parallels
Decrease with high latitudes

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5
Q

Longitude

A

The angular distance east to west of the Prime Miridian

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6
Q

Prime Meridian

A

Line of longitude setting 0 for east-west
Thru Greenwich

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7
Q

Meridian

A

A line joining all points that have the same longitude
All great circles

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8
Q

Graticules

A

The grid formed by parallels and meridians
Converge at right angles

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9
Q

Shortest distance on a sphere

A

an arc of a great circle

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10
Q

Azimuth

A

Direction on a globe (sphere)
Angle measured clockwise from true north-south line and great circle path

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11
Q

Loxodrome/Rhumb Line

A

A line of constant bearing (compass direction)
Eventually leads you to a pole

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12
Q

4 phases to map projection from reality

A

Geoid
Ellipsoid (reference)
Nominal, reference globe
Map Projection

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13
Q

Projection

A

Method of representing data from a curved surface onto a flat plane
Systematic and orderly method

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14
Q

General projection errors to graticules

A

Tearing
Compression
Shearing

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15
Q

4 Projection Distortion Properties (sort of classifications)

A

Equivalence
Conformal
Equidistant
Azimuthal
Composite

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16
Q

Map Projection Distortion Properties: Equivalence

A

Area
Preserve area, distort shape

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17
Q

Map Projection Distortion Properties: Conformal

A

Shape
actually local angle, not exactly shape
True-Shape, scale is the same in all directions about point

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18
Q

Map Projection Distrotion Properties: Equidistance

A

Distance
Distance is true along standard parallel

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19
Q

Map Projection Distortion Properties: Azimuthal

A

Distance is correct only from the center

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20
Q

Composite Map Projections

A

Combines elements of other projection properties to minimize errors
Its a compromise
Distorts everything a little

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21
Q

Map Projection Classes/Geometry
(Developable Surfaces)

A

Conic
Cylindrical
Azimuthal (Planar?)

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22
Q

Classifications of Projections
Map projections can be defined by their…?

A

Distortions (equidistant, conformal, etc)
Class/Geometry (Conic, cylindrical, etc)
Point of Secancy
Aspect

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23
Q

Cylindrical projection at equatorial aspect

A

Parallels and meridians are straight lines
Meridians are orthogonal to parallels and uniformly spaced

24
Q

Conic projections in the polar aspect

A

All parallels are concentric arcs of circle
Meridians are straight lines, perpendicular to every parallel and uniformly spaced

25
Q

Azimuthal in polar aspects

A

All parallels are circular
Meridians are straight lines, uniformly spaced

26
Q

Cylindrical projection common use

A

Entire world

27
Q

Conic projection common limitation/use

A

Can only show one hemisphere

28
Q

3 types of azimuthal projections

A

Orthographic
Stereographic
Gnomonic

29
Q

Orthographic projection (azimuthal)

A

The light source is an infinite distance
Used for perspective view of hemispheres
Distorts area and shape

30
Q

Stereographic projection (azimuthal)

A

Light source is antipode
Specific purpose of maintaining shape (conformal)
Useful for areas extending equally in all directions (Asia)

31
Q

Gnomonic projection (azimuthal)

A

Light emanates from center of globe
Displays all great circles as straight lines

32
Q

Pseudo-cylindrical or conic projection

A

Meridians are arbitrarily curved
Primary accuracy is usually only preserved along standard parallel

33
Q

Map projections compromise between…

A

Conformality, equivalence, and equidistance

34
Q

Developable surfaces

A

A surfaces that can be flattened out without tearing or distortion

35
Q

Standard line/parallel/point

A

The point or line that is correct on a projections
Distortion increases the further you go from these areas

36
Q

Area of least deformation

A

Areas of minimum distortion surrounding the standard parallel or point

37
Q

Map Projection Classification: Secancy vs Tangency

A

does the developable surface touch the globe as a point secancy or point of tangency

38
Q

Secant case

A

the developable surface for projection intersects the globe, there are two standard lines
Distortion decreases both inward and outward from standard lines
Least distortion at points of contact
Transverse Mercator

39
Q

Tangent case

A

The developable surface for projection touches the globe, only one standard line
Distortion increases as globe curves, away from tangent point

40
Q

Map Projection Aspect

A

The direction of the projection’s plane orientation
Normal
Polar
Equatorial
Transverse
Oblique
Choice of aspect is informed by location and orientation of focus area

41
Q

Transverse Aspect

A

Line of tangency oriented along meridian rather than equator
Developable surface on its side (compared to normal)
Great circle formed by a pair of opposing meridians

42
Q

Oblique Aspect

A

Developable surface is angled (compared to normal)
Standard point/parallel is not poles or equator

43
Q

Equatorial Aspect

A

Developable surface is placed so north-south is up-down

44
Q

UTM

A

Universal Transvers Mercator
Secant case
Projected coordinate system
Conformal

45
Q

UTM x-axis

A

North Hemisphere @ equator
South Hem @ 10mil meters from equator

46
Q

US UTM Zones

A

10 - 19 for lower 48
1 - 10 for Alaska
4 and 5 for HI

47
Q

State Plane

A

Projected coordinate system
uses feet
but sometimes meters?
N-S and E-W are perpendicular
120 zones
Small Zones = Higher accuracy

48
Q

3 Projections used for State Plane

A

All conformal
Lambert Conformal Conic (E-W)
Transverse Mercator (N-S)
Oblique Mercator (some of Alaska)

49
Q

State Plane: False Easting

A

Moves Y axis westward so all X values are positive
Lambert - 600k meters west of CM
Mercator - 200k meters west of CM

50
Q

Tissot’s Indicatrix

A

Quantifies and visualizes map distortions
Uses uniform circles to illustrate linear, angular, and areal distortions

51
Q

3 Primary Factors in Picking a Projection

A

Shape of the area
Location and Orientation of the area
Purpose of the map

52
Q

Possible purposes to chose Conformal projection

A

Maps that preserve shape
Measuring angles
Showing accurate location directions
Representing the shape of an area
Topographic, cadastral, navigation, military

53
Q

Possible purposes to chose Equivalence projection

A

Maps that preserve area
Density of an area (Population)
Spatial extent (Land Use)
Quantitative measure by area (GDP by country)

54
Q

Possible purposes to chose Azimuthal Equidistant projection

A

Maps that preserve scale*
Airline distances
Seismic maps
Cost based on straight line distance
*Scale only preserved from standard point

55
Q

Possible purposes to chose Azimuthal projection

A

Maps that preserve direction

Cartography (6 decks)

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