Convergency and Conversion Angle Flashcards
Earth convergency:
Convergency increases -
with the -
away from the equator towards the poles
sine of the latitude
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-
d’long x sine of latitude
d’long = the difference in longitude
Earth convergency:
If the two positions are at different latitudes, the formula for the approximate convergency becomes -
d’ long x sin mean latitude
Earth convergency:
Position A is at 30° 25’ W and position B is at 45° 25’ W
What is the d’long?
When both values are W or E, find the difference.
= 15° W
Earth convergency:
Position A is at 30° 25’ W and position B is at 45° 25’ E
What is the d’long?
When both values are not the same side of the greenwich meridian, add the two values.
= 75° 50’
Conversion angle =
1/2 convergency
Relevant to conversion angle:
Convergency =
2 conversion angle
All maps and charts used for aviation except mercator, will show a great circle as a -
and the rhumb line as a -
straight line
curved line towards the equator
The mercator chart shows the rhumb line as a -
And the great circle as a -
straight line
curve towards the nearer pole
If a curve exist, a great circle curve will always curve towards the -
poles
If a curve exist, a rhumb line curve will always curve towards the -
equator
Regardless if it’s plotted on a globe, mercator, or lambert. A rhumb line will always cut the meridians at -
a constant angle
Regardless if it’s plotted on a globe, mercator, or lambert. A great circle line will always cut the meridians at -
a consistently changing angle(due to convergence)
Parallels of latitude always cut meridians at -
90 degrees
To be able to qualify as a great circle, it must cut the -
centre of the earth(share it’s radius)
To be able to qualify as a rhumb line, it must cut -
meridians at a constant angle
Mean latitude:
What is the mean latitude between 45N and 15N?
45 + 15 = 60 / 2 = 30 degrees
Mean latitude:
What is the mean latitude between 35N and 15S?
Because it’s opposite hemispheres, subtract the one from the other and divide it by two.
How will you write a longitude diagram with a top view of the globe?
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.
How will you write a latitude diagram with a side view of the globe?
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.
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 -
it could not cut all the meridians (which are at different angles to each other) at the same angle.
Regardless of the type of chart:
A great circle track is a consistently -
A great circle track cuts each consecutive meridian -
changing track
At a different angle
Regardless of the type of chart:
A rhumb line track is a constant -
A rhumb line cuts each consecutive meridian -
track
At a constant angle
The mnemonic to remember great circle changing angle with each meridian -
DIID
Or on paper:
DI
ID
