ATPL General Navigation
Convergency Formula - answer= Change in Long x Sin (mean lat)
Departure Formula - answer= Change in Long x Cos (mean lat)
What shape is the Earth? - answerOblate spheroid or ellipsoid
What is a Rhumb line? - answerA line which crosses each meridian at a constant angle,
so has a constant track. Includes parallels of latitude.
What is a Great circle? - answerThe largest possible circle around the Earth whose
centre passes through the centre of the Earth - includes all meridians and the equator.
The track (relative path angle to north) along a great circle is constantly changing when
not moving along a meridian or the equator.
The equator can be what type(s) of lines? - answerA rhumb line and a great circle
In which directions do the meridians point? - answerNorthward. They diverge at the
South Pole and converge at the North Pole.
What is the circumference of the Earth? - answer40,000 km or 21,600 nm
Radius of Earth (Average) - answer6366 km or 3437 nm
Radius of the Earth at the equator - answer6,378 km or 3440 nm
Radius of the Earth at the Poles - answer6357 km or 3430 nm
Semi major radius & semi minor radius conversion - answerSemi-major to semi-minor
= / 1.0033
Semi-minor to semi-major = x 1.0033
Geocentric Latitude - answerThe angle between a line drawn from a point on the
surface to the Earth's centre and the plane of the Equator.
Geodetic/Geographic Latitude - answerThe angle between a perpendicular line drawn
from a point on the Earth's surface and the equator.
Due to the oblate spheroid shape of the Earth, the line will pass near, but generally not
through the centre of the Earth.
, The latitude where the greatest difference between geodetic and geocentric occurs and
the error in minutes of arc. - answer45° North/South, 11.6 minutes of arc.
1 nautical mile = ? kilometres - answer1.852
1 nautical mile = ? feet - answer6080
1 nautical mile = ? statute miles - answer1.15
1 kilometre = ? feet - answer3280
1 meter = ? feet - answer3.28
1 minute of arc latitude in nautical mile - answer1 nmi
Also equals 1nmi along the equator's longitude but gets shorter towards the poles.
(Departure equation)
3 chart projections - answerDirect Mercator - cylindrical
Lamberts - conical
Azimuthal or plane (stereographic)
Where on a direct Mercator chart is the chart orthomorphic? - answerThe chart is
orthomorphic close to the equator.
Is the lamberts conical chart orthomorphic? - answerThe chart is very Nnearly
orthomorphic.
Is the polar stereographic chart orthomorphic? - answerThat chart is very nearly
orthomorphic at the poles.
Where is the scale correct on a direct Mercator chart? - answerThe scale is correct at
the Equator or parallel of origin.
Where is the scale correct on a lamberts conical chart? - answerThe scale is correct at
the standard parallels.
Where is the scale correct on a polar stereographic chart and where does it change? -
answerThe scale is correct at the poles, but expands outwards.
Where does the scale expand on a direct Mercator? - answerThe scale expands at the
secant of the latitude.
How does the scale vary on a lamberts conical chart? - answerThe scale expands
outside the standard parallels and contracts within.
Convergency Formula - answer= Change in Long x Sin (mean lat)
Departure Formula - answer= Change in Long x Cos (mean lat)
What shape is the Earth? - answerOblate spheroid or ellipsoid
What is a Rhumb line? - answerA line which crosses each meridian at a constant angle,
so has a constant track. Includes parallels of latitude.
What is a Great circle? - answerThe largest possible circle around the Earth whose
centre passes through the centre of the Earth - includes all meridians and the equator.
The track (relative path angle to north) along a great circle is constantly changing when
not moving along a meridian or the equator.
The equator can be what type(s) of lines? - answerA rhumb line and a great circle
In which directions do the meridians point? - answerNorthward. They diverge at the
South Pole and converge at the North Pole.
What is the circumference of the Earth? - answer40,000 km or 21,600 nm
Radius of Earth (Average) - answer6366 km or 3437 nm
Radius of the Earth at the equator - answer6,378 km or 3440 nm
Radius of the Earth at the Poles - answer6357 km or 3430 nm
Semi major radius & semi minor radius conversion - answerSemi-major to semi-minor
= / 1.0033
Semi-minor to semi-major = x 1.0033
Geocentric Latitude - answerThe angle between a line drawn from a point on the
surface to the Earth's centre and the plane of the Equator.
Geodetic/Geographic Latitude - answerThe angle between a perpendicular line drawn
from a point on the Earth's surface and the equator.
Due to the oblate spheroid shape of the Earth, the line will pass near, but generally not
through the centre of the Earth.
, The latitude where the greatest difference between geodetic and geocentric occurs and
the error in minutes of arc. - answer45° North/South, 11.6 minutes of arc.
1 nautical mile = ? kilometres - answer1.852
1 nautical mile = ? feet - answer6080
1 nautical mile = ? statute miles - answer1.15
1 kilometre = ? feet - answer3280
1 meter = ? feet - answer3.28
1 minute of arc latitude in nautical mile - answer1 nmi
Also equals 1nmi along the equator's longitude but gets shorter towards the poles.
(Departure equation)
3 chart projections - answerDirect Mercator - cylindrical
Lamberts - conical
Azimuthal or plane (stereographic)
Where on a direct Mercator chart is the chart orthomorphic? - answerThe chart is
orthomorphic close to the equator.
Is the lamberts conical chart orthomorphic? - answerThe chart is very Nnearly
orthomorphic.
Is the polar stereographic chart orthomorphic? - answerThat chart is very nearly
orthomorphic at the poles.
Where is the scale correct on a direct Mercator chart? - answerThe scale is correct at
the Equator or parallel of origin.
Where is the scale correct on a lamberts conical chart? - answerThe scale is correct at
the standard parallels.
Where is the scale correct on a polar stereographic chart and where does it change? -
answerThe scale is correct at the poles, but expands outwards.
Where does the scale expand on a direct Mercator? - answerThe scale expands at the
secant of the latitude.
How does the scale vary on a lamberts conical chart? - answerThe scale expands
outside the standard parallels and contracts within.
