Aeronautical Charts

Question 1

Orthomorphism

Answer 1

Relates to ideal properties of a chart.
Bearings on a chart represent bearings on the earth, shapes should be correctly represented, great circles and round lines both straight, scale to be correct and constant at all points on the earth, longitude and latitude across at 90°angle.

For navigation purposes a chart must be orthomorphic. -parallels of latitude and meridians of longitude must be at right angles, as they are on the earth.
-scale needs to be correct. Scale must be the same from a point north south AND east west.

Question 2

Mercator chart

Answer 2

Cylindrical projection. Remline straight, great circles appear to curve convex to nearest pole, or concave to equator.

Used mostly in equatorial regions, where scale is constant.

MRS CONVEX POLE. EQUATOR SCALE CORRECT

Question 3

Lambert conformal conic projection chart

Answer 3

Carole king placed on top of earth with light source projected from the center. Benefit is that poles are projected

This projection cuts its surface at two points, these two points are called standard parallels.
First scale between two parallels, where scale is slightly contracted eg. earth distance is greater than measured distance.

For practical purposes scale is considered equal over this whole chart.

Question 4

Properties of Lambert chart

Answer 4

Rhumb line is curved- concave to the poles, convex is to equator.
Great circle is straight, easily plotted

Used an aviation, distances are easily measured due to constant scale and used for mid latitude navigation.

Question 5

Polar stereographic projection

Answer 5

Parallels of latitude are concentric circles
Meridians of longitude are straight lines, radiating like bike spokes from the center

Scale is true at origin with scale and distortion increasing with distance from the origin
Direction is accurate from the origin

Only chart where great circles are concave to the poles, unless they run through the pole.

Question 6

Departure formula

Answer 6

DEPARTURE FORMULA ALWAYS GIVES RHUMBLINE DISTANCE

Used to calculate distances on parallels of latitude, other than on the equator where one degree equals 60NM.

∆long (minutes) cos LAT.

MINUTES CAUSE YOU LATE!

Question 7

Scale correct where?

Answer 7

Standard parallels on Lambert

Question 8

Earth C-O-nversion correct where?

Answer 8

Parallels of O-rigin

Question 9

Earth convergency

Answer 9

Difference in curvature of the earth between two points,

In Northern hemisphere.
West to east add convergency, east to west subtract convergency

Southern hemisphere
West east subtract convergency, east to west add convergency

Important to draw up diagram with converging meridians superimposed.

Question 10

Conversion angle

Answer 10

angular Difference between rhumb line and great circle track.
Half of convergency angle.
Used when plotting on mercator chart..

In northern hemisphere, at the beginning of track, point a, heading to to maintain great circle track will be greater than Ram line track by conversion angle, however, at the end of the track, heating will be less than Ram line track by the conversion line.

Ie. Double conversion angle (convergency value) is the change in heading from point a to point b to MAINTAIN GCT.

Question 11

Great circle vs rhumb line

Answer 11

North hemisphere, great circle always lie to the north of a rhumbline.
Southern hemisphere, great circle will always lie to the south of Rhumb line.

Great circle always lies poleward of Rhumb line