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Navigation > Nav 07 - 09 - Map Projections > Flashcards

Nav 07 - 09 - Map Projections Flashcards

1
Q

Review Questions

What is the definition of Latitude?

A

Angular distance from the equator measured along a Meridian

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2
Q

Review Questions

What is the definition of Longitude

A

A semi-Great Circle of the surface of the Earth joining the poles of the earth

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3
Q

What is a map?

A

A small scale, flat surface representation of some portion of the earth’s surface

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4
Q

Define Conformality

A

The correct representation of angles

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5
Q

For a map to be conformal, what must be met?

A

Meridians and parallels must intercept at right angles

Scale must be the same in all directions or change at a constant rate

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6
Q

Define Orthomorphism

A

Shapes are correctly defined

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7
Q

To possess correct shape, a map must be:

A

Conformal

Scale must be the same in all directions

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8
Q

True or false

It is difficult to keep the scale constant over an entire surface, but it can be considered correct over small areas.

A

False, it is impossible to keep the scale constant over an entire surface

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9
Q

Define Scale

A

A ratio of given distance on a map to the actual distance on the earth

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10
Q

What are the methods of expressing scale?

A

Representative fraction

Statement in words

Graduated scale

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11
Q

A 1 : 500 000 map is what size of scale, show what size of area, and show more of what compared to a 1 : 1 000 000 map?

A

A 1 : 500 000 map is a large scale, shows a smaller area and more detail than a 1 : 1 000 000 map, which show a larger area with less detail.

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12
Q

The three types of map projections in general use are?

A

Cylindrical
Conical
Azimuthal / Tangential

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13
Q

A Mercator projection is derived from what map projection?

A

Cylindrical

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14
Q

On a Mercator projection, a Rhumb line and a Great circle are illustrated how?

A

A Rhumb line is straight, a Great circle is curved and convex towards nearer pole.

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15
Q

Describe the following Mercator Projection properties.

Parallels
Meridians
Scale
Shapes
Great Circle
Rhumb Line
A

Parallels: Straight lines, unequally spaced
Meridians: Straight lines, parallel, equally spaced
Scale: Correct at equator, expands away from equator
Shapes: Preserved (approx) near equator, but distorts increasingly away from equator.
Great Circle: Curved, convex to nearer pole
Rhumb Line: Straight lines

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16
Q

What are the limitations of the Mercator Projection map?

A

Excessive scale expansion

Enormous area distortion in higher latitudes

Great Circles are plotted as curved lines

17
Q

What are the other cylindrical projections (apart from standard cylindrical)?

A

Transverse Mercator

Oblique Mercator

18
Q

A Transverse Mercator map is useful for what routes?

A

North-South routes along a given meridian.

19
Q

True or false

An Oblique Mercator map is used to show regions along a Great Circle other than the Equator or a particular meridian of longitiude.

A

True

20
Q

What type of map is a Oblique Mercator used to create?

A

A strip map

21
Q

Points along a strip map retain all the advantages of the Mercator at the ________.

A

Equator

22
Q

The line of tangency on a strip map is a straight line and is a (Rhumb line or Great Circle)?

A

Great Circle

23
Q

The Lambert Conformal projection is a variation of what projection?

A

Conical

24
Q

How many points of tangency does a Lambert Conformal map have?

A

2 points of tangency

25
Q

Describe the following Lambert Conformal Properties

Parallels
Meridians
Scale
Shapes
Great Circles
Rhumb lines
A

Parallels: Concentric circles meet meridians at right angles
Meridians: Straight lines meet at the pole
Scale: Correct at two standard parallels (SP)
Between SPs: contracts
Outside SPs: Expands
Considered correct over a single sheet
Shapes: Approximately preserved everywhere
Great Circles: Approximately straight lines
Rhumb lines: Concave to nearest pole

26
Q

What are some limitations of the Lambert Conformal?

A

Limited to use near the Standard Parallels, due to distortion that happens as you move away from SPs
Good choice for mid-latitude countries like Canada
Many charts used in RCAF are Lambert Conformal
VNC, ONC, JNC

27
Q

Polar stereo maps are which type of projection?

A

Azimuthal

28
Q

Describe the following Polar Stereo Properties

Parallels
Meridians
Scale
Shapes
Great Circles
Rhumb lines
A

Parallels: Concentric, unequally spaced circles concave to nearest pole
Meridians: Straight lines, converging at the pole (like spokes on a bike tire)
Scale: Expands equally in all directions away from the pole
Shapes: Correct around point of tangency, distorted elsewhere
Great Circles: Approximately straight lines in polar region
Rhumb lines: Concave to nearest pole

29
Q

In what latitudes are Polar Stereographic maps used? Why?

A

Used in high latitudes only, 45° - 90°

Below 45° there is too much distortion to be a viable tool

30
Q

What are the desirable map properties?

A 
Great Circles - Straight lines
Rhumb lines - Straight lines
Angles - Correct
Shape - Correct
Size - Correct
Scale Correct and constant
31
Q

The following charts have what in common?

Global Navigation and Planning Chart (GNC)
Jet Navigation Chart (JNC)
Operational Navigation Chart (ONC)
VFR Navigation Chart (VNC)

A

They are all used in the RCAF and are all Lambert Conformal projections (conical)

32
Q

A GPH 206/ 207 are for what altitudes and are what projections? Are they used on IFR flights?

A

GPH 206 - Low altitude and Lambert Conformal
GPH 207 - High altitude and Lambert conformal

Used on IFR flights

33
Q

Review Questions

What are the desirable map properties?

A 
Great Circles - Straight lines
Rhumb lines - Straight lines
Angles - Correct
Shape - Correct
Size - Correct
Scale Correct and constant
34
Q

Review Questions

What are some plotting charts used in the RCAF?

A 
GNC 
ONC
JNC
VNC
GPH 206 / 207

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