Navigation Theory Flashcards
Viewed from above, what direction does the Earth spin?
Anti-clockwise.
What format of Lat/Long does the military use?
DMM
Degrees, Minutes, Decimal minutes
What is the definition of a nautical mile?
A nautical mile is equal to 1 minute of latitude along any line of longitude.
What is a great circle?
A great circle is a circle on the surface of a sphere whose centre and radius are those of the sphere itself. The shortest distance between any two points on the surface of a sphere is the smaller arc of the great circle joining them.
What is a Rhumb line?
A regular curve that will cut all meridians at the same angle. The advantages include that direction is constant, it is usable for distances <1000nm but it gives a longer track distance than a great circle route for distances >1000nm.
What is 1nm in feet?
6076 ft
What is 1nm in metres?
1852 m
What is Magnetic Variation?
Magnetic variation is the angular difference between true north and magnetic north at any given point on the Earth’s surface.
To convert true track into magnetic direction, local variation must be applied using the rules…
Variation East, Magnetic Least
Variation West, Magnetic Best
What are Isogonals?
Isogonals connect points of equal magnetic variations.
What acronym explains how to change from one bearing to the next?
CDMVT
Cadbury’s Dairy Milk is Very Tasty
Compass bearing becomes the Magnetic bearing with the application of deviation
The magnetic bearing, is separate from the true bearing by variation.
What is a Geoid?
Geoid
Physical model of the Earth and approximates to MSL
Blue- Geoid
Red- Elipsoid
Yellow- Sphere
What is the difference between perspective and non-perspective projections?
Perspective
True, geometric projections, drawing shadoes which are cast by meridians and parallels on a transparent model of Earth onto a plane surface.
Non-perspective
Also known as mathematical perspective.
If the point of tangency is 45° N/S then the apex angle is ?
If the point of tangency is 60° N/S then the apex angle is ?
45° N/S, Apex Angle = 90
60° N/S, Apex Angle = 120
What are the three types of azimuthal projection?
Polar
Equatorial
Oblique
What types of Mercator projections are there?
General - Upright projection, used along areas on the Equator
Plane/Oblique - User for regions along great circles other than the Equator.
Transverse - used for areas along the poles.
What are False Northing and False Easting?
False easting is a linear value applied to the origin of the x coordinates. False northing is a linear value applied to the origin of the y coordinates.
What is MGRS?
Military Grid Reference System
MGRS is a grid reference system designed to be used with the UTM and UPS grids.
For example:
4QFJ12345678
4Q (grid zone designator, GZD)
FJ (the 100,000-meter square identifier)
12345678 (numerical location; easting is 1234 and northing is 5678)