Lambert's Conformal Projection

Question 1

Regarding conic projections, what is chart convergency proportional to?

Answer 1

Parallel of origin.

The higher its latitude, the greater the convergency.

Question 2

On a Lambert’s conformal conical projection, what determines the usable area?

Answer 2

The usable area usually falls between the two standard parallels.

Question 3

On a Lambert’s conformal conic chart, what is the latitude range of usable area?

Answer 3

24° (to keep scale errors below 1 %).

Question 4

How to calculate the parallel of origin from the standard parallels?

Answer 4

Add the standard parallels and divide them by two.

The parallel of origin is assumed to be the average of standard parallels.

Question 5

How do:

(a) parallels of latitude

(b) meridians of longitude

appear on a Lambert’s conformal conic chart?

Answer 5

(a) arcs of concentric circles around a pole
(b) straight lines converging on the apex

Question 6

Regarding Lambert’s conformal conical projection, where is the scale correct?

Answer 6

At either standard parallel.

Question 7

How is the:

(a) internal

(b) external

cone used in Lambert’s conformal conical projections called?

Answer 7

(a) secant cone
(b) tangent cone

Question 8

Describe the ideal properties of:

(a) convergency

(b) scale

(c) great circle tracks

on Lambert’s conformal conic charts.

Answer 8

Provided that the standard parallels are correctly chosen:

(a) chart convergency = earth convergency
(b) scale is constant
(c) great circles are straight lines

Question 9

What does the convergence factor equal?

Answer 9

The sine of the parallel of origin.

Question 10

Regarding Lambert’s conformal conical projection, how does the cone distance vary from the reduced Earth distance?

Answer 10

(a) contracts on the internal cone
(b) expands on the external cone

Question 11

Define: chart convergency.

Answer 11

The change in great circle bearings between two positions.

Question 12

On Lambert’s conformal conic charts, how does scale error vary?

Answer 12

It increases with increasing distance from standard parallels.

Question 13

How to calculate the conversion angle on a conic chart?

Answer 13

CA = (∆λ · n) / 2

Question 14

What is an alternative name for the convergence factor (on conic charts)?

Answer 14

Constant of the Cone.

Question 15

How does the convergence factor change with varying latitude?

Answer 15

It doesn’t. It is constant.

Question 16

Describe: the function of the Radio Magnetic Indicator.

Answer 16

It indicates the magnetic great circle track to an NDB.

Question 17

How do rhumb line tracks and great circle tracks appear on Lambert’s conformal conic charts?

Answer 17

Rhumb lines are concave to the nearer pole.

Great circles are concave to the parallel of origin but assumed straight.

Question 18

On Lambert’s conformal conic charts, how does the convergency vary with latitude?

Answer 18

It doesn’t.

Chart meridians are straight lines so the convergency is the same all over the chart.

Question 19

How does the Lambert’s conformal conical projection solve the problem of thin usable area in simple conical projections?

Answer 19

By lowering the cone so that it cuts into the Earth.

Question 20

How can we calculate the chart convergency on a Lambert’s conformal conic chart?

Answer 20

Chart convergency = ∆λ · n

Question 21

What limits the usefulness of simple conic projections?

Answer 21

Small (long and narrow) area of constant scale.

Question 22

Describe: convergence factor.

Answer 22

A standard measure of convergency.

It depends on the parallel of origin.

It equals the sine of the parallel of origin.

Another name for it is the constant of the cone.

Symbol: n.

Question 23

Define: complex curve.

Answer 23

An S-shaped great circle track on a conic chart, where it crosses the parallel of origin.

Question 24

Define: standard parallels.

Answer 24

Small circles along which the secant cone intersects the reduced Earth’s surface.

Question 25

How does the scale denominator vary as scale:

(a) expands

(b) contracts

?

Answer 25

(a) reduces
(b) increases

Question 26

When performing RMI calculations, where should magnetic variation be applied?

Answer 26

At the aircraft, because NDBs emit omnidirectional signals which are not bearing-specific.

Question 27

Is the parallel of origin equidistant from the standard parallels?

Answer 27

No, it is slightly closer to the pole.

However, it is acceptable to assume that it is since the deviation is minimal.

Question 28

Which areas do Lambert’s conformal conic charts fit the best?

Answer 28

Mid-latitudes.

Question 29

Conventionally, diagrams include westerly meridians on the left and easterly meridians on the right. When do we indicate them in the opposite sense?

Answer 29

When the tracks on our diagrams cross E/W 180° (shorter route).

Question 30

What is the maximum value of magnetic variation that can be applied to relative bearing indications?

Answer 30

Magnetic variation is not applied to relative bearings.

Question 31

Regarding conic projections, where does chart convergency equal Earth convergency?

Answer 31

At the parallel of origin.

Question 32

Define: the parallel of origin.

Answer 32

If we take that the parallel of origin is a derivate of a line parallel to the secant cone at a tangent to the Earth’s surface, then the parallel of origin is defined by the latitude of the tangent.

Question 33

Where rhumb lines and great circles curve in the same sense, do they coincide?

Answer 33

No, rhumb lines are on the equatorial side of great circles.

Question 34

Regarding Lambert’s conformal conic charts, how does scale change:

(a) in direction from standard parallels toward the parallel of origin

(b) in direction from standard parallels away from the parallel of origin

?

Answer 34

(b) scale contracts
(a) scale expands

Question 35

Regarding Lambert’s conformal conical projection, where does the greatest scale contraction occur?

Answer 35

Halfway between the standard parallels.

Question 36

Regarding Lambert’s conformal conical projections, what is the straightness of great circle tracks proportional to?

Answer 36

To the difference between the standard parallels.

The closer they are, the straighter the great circle tracks.