Convergency and Conversion Angle

Question 1

Earth convergency:

Convergency increases -

with the -

Answer 1

away from the equator towards the poles

sine of the latitude

Question 2

Earth convergency:

If the convergency between two positions other than at the pole is required, provided both positions are at the same latitude the following formula can be used-

Answer 2

d’long x sine of latitude

d’long = the difference in longitude

Question 3

Earth convergency:

If the two positions are at different latitudes, the formula for the approximate convergency becomes -

Answer 3

d’ long x sin mean latitude

Question 4

Earth convergency:

Position A is at 30° 25’ W and position B is at 45° 25’ W

What is the d’long?

Answer 4

When both values are W or E, find the difference.

= 15° W

Question 5

Earth convergency:

Position A is at 30° 25’ W and position B is at 45° 25’ E

What is the d’long?

Answer 5

When both values are not the same side of the greenwich meridian, add the two values.

= 75° 50’

Question 6

Conversion angle =

Answer 6

1/2 convergency

Question 7

Relevant to conversion angle:

Convergency =

Answer 7

2 conversion angle

Question 8

All maps and charts used for aviation except mercator, will show a great circle as a -

and the rhumb line as a -

Answer 8

straight line

curved line towards the equator

Question 9

The mercator chart shows the rhumb line as a -

And the great circle as a -

Answer 9

straight line

curve towards the nearer pole

Question 10

If a curve exist, a great circle curve will always curve towards the -

Answer 10

poles

Question 11

If a curve exist, a rhumb line curve will always curve towards the -

Answer 11

equator

Question 12

Regardless if it’s plotted on a globe, mercator, or lambert. A rhumb line will always cut the meridians at -

Answer 12

a constant angle

Question 13

Regardless if it’s plotted on a globe, mercator, or lambert. A great circle line will always cut the meridians at -

Answer 13

a consistently changing angle(due to convergence)

Question 14

Parallels of latitude always cut meridians at -

Answer 14

90 degrees

Question 15

To be able to qualify as a great circle, it must cut the -

Answer 15

centre of the earth(share it’s radius)

Question 16

To be able to qualify as a rhumb line, it must cut -

Answer 16

meridians at a constant angle

Question 17

Mean latitude:

What is the mean latitude between 45N and 15N?

Answer 17

45 + 15 = 60 / 2 = 30 degrees

Question 18

Mean latitude:

What is the mean latitude between 35N and 15S?

Answer 18

Because it’s opposite hemispheres, subtract the one from the other and divide it by two.

Question 19

How will you write a longitude diagram with a top view of the globe?

Answer 19

The prime meridian will be at the bottom at 000 degrees. The Ante prime meridian will be at the top at 180 degrees. E and W will both have a 90 degree angle. From 000 both angles increase in value towards the APM, and end with 180 degrees at the APM. This will make visualisation much easier.

YOU ARE LOOKING AT THE EARTH FROM THE TOP, THE CENTRE BEING THE NORTH POLE.

Do not confuse this view with that of a compass rose.

Question 20

How will you write a latitude diagram with a side view of the globe?

Answer 20

The top will be the north pole, the south pole the bottom. Latitude increase towards the pole. 0 degrees will be on the left and right, 90 degrees at the top.

This make latitude problems much easier.

YOU ARE LOOKING AT THE GLOBE FROM THE SIDE, THE NORTH AND SOUTH POLE AND THE TOP AND BOTTOM RESPECTIVELY.

Question 21

At any point on the Earth, True North is defined with reference to the direction of the local meridian. If you are at a different meridian in flight from the point at which you started, your local direction of True North has changed. This is the reason why a rhumb line is a continuously curved line on the Earth’s surface. If it did not constantly curve -

Answer 21

it could not cut all the meridians (which are at different angles to each other) at the same angle.

Question 22

Regardless of the type of chart:

A great circle track is a consistently -

A great circle track cuts each consecutive meridian -

Answer 22

changing track

At a different angle

Question 23

Regardless of the type of chart:

A rhumb line track is a constant -

A rhumb line cuts each consecutive meridian -

Answer 23

track

At a constant angle

Question 24

The mnemonic to remember great circle changing angle with each meridian -

Answer 24

DIID

Or on paper:

DI
ID

Question 25

On a mercator, the great circle will be a -

Answer 25

curved line with a consistently changing track

Question 26

On a mercator, the rhumb line will be a -

Answer 26

A straight line with a constant track

Question 27

The difference between a rhumb line and a great circle track is the -

Answer 27

conversion angle

Question 28

When calculating the angle change between consecutive meridians of a great circle, which formula should be used?

Answer 28

The convergency formula

Question 29

When calculating the difference between a rhumb line and a great circle, which formula should be used?

Answer 29

The conversion angle formula(which requires convergency)

Question 30

The reciprocal of a rhumb line is -

Answer 30

valid

Question 31

The reciprocal of a great circle track -

Answer 31

is not valid