Nav Definitions

The flashcards below were created by user glennrooke on FreezingBlue Flashcards.

1. Great circle
Circle whos radius is that of the earth and whose plane passes through the centre of the earth.

the shorter arc is the shortest distance between any two points
2. Small Circle
Any circle on the surface whose radius is not that of the earth.
3. Rhumb Line
A regular curved line which cuts all Meridians at the same angle
4. True Poles
• The extremities of the spin axis of the earth
• Where all meridians meet
5. Parallel of Latitude
• All Small Circles (other than equator)
• All Rhumb Lines
6. Prime Meridian
• Also known as Greenwich Meridian
• Semi-Great circle passing through the poles and through Greenwich
• Defines Longitude 00 East or West
7. Anti-Meridian
• Lies at 1800 degrees removed east/west from the Meridian in question
• Prime Anti-meridian is at exactly 180 east/west of Greenwich
8. International Dateline
Kind of follows 180 meridian
9. Graticule
X Y grid formed by the meridian, equator and parallels of lattitude
10. Variation
Difference between true direction and Magnetic direction

Variation is east when Mag north lies East of True North

Variation is west when Mag north lies West of True North
11. Isogonals
Lines joining points of equal Variation
12. Deviation
• A/C specific error in compass.
• Compass Swing performed
• Compass direction +/- deviation gives magnetic direction

Deviation is east when Compass north lies East of Mag North

Deviation is west when Compass north lies East of Mag North
13. Does 1 degree of longitude equal 60 miles?
Only at the equator. Always true for latitude though.
14. Departure Formula
• Distance = d Long x Cos lat

Only valid for points at the same Latitude!

15. Earth Convergence Formula
The angle of inclination between any two meridians at a given Latitude.

Change of Long(deg) x sin mean Lat
16. How does Wind effect distance to PNR and ETP?
ETP always moves into the wind.

PNR reduces in any wind compared to Nil wind conditions
17. What Fuel Profile gives the PNR furtherest away
Best Range Speed
18. How does Air Density affect TAS
TAS will increase with lower density

Increase in height, or an increase in ambient temp and same height.
19. What Grid referencing system is used for GNSS and FMS
WGS84

World Geodesic system 1984

"Geod" meaning the earth shape
20. when using departure formula to get Distance between two points on same parallel is the answer a Rhumb Line or great circle
Rhumb Line
21. What is the conversion angle
Difference between the Rhumb line track and the true track at the start and end of the lines.

Equal to half the earth convergence.

= 0.5 x d.long sin mean latitude
 Author: glennrooke ID: 234373 Card Set: Nav Definitions Updated: 2013-09-18 02:17:35 Tags: Definitions Folders: Description: Definitions Show Answers: