Navigation Basics Flashcards
What is the form of the Earth?
Oblate spheroid
What is the definition of a great circle?
A circle on the surface of a sphere, whose centre, and radius are that of the sphere itself.
What is a rhumb line?
A regularly curved line on the surface of the Earth that cuts all meridians at the same angle. They are convex to the equator and are always longer (or equal to) the great circle track between two places
What is a nautical mile?
Length of a great circle that subtends 1 minute at the center of the earth. E.g. 60nm is one degree of longitude/latitude
Distance conversions:
Nm, km, sm, in, cm, ft
2.54cm per inch 12in per ft 6076ft per nm 5280ft per nm 1853m per nm
What is departure?
Distance between two points on the same parallel, but on different meridians.
Departure = CHLONG (minutes) * cos(latitude)
What is convergence?
The angle of inclination between 2 selected meridians. It is 0 at the equator and increases towards the poles.
What degree of inclination is the earths equator to the plane of orbit?
23.5 degrees
When are the equinoxes and the solstices?
In Southern Hemisphere: Autumn equinox = 21 March Winter solstice = 21 June Spring equinox = 22 September Summer solstice = 22 December
How many degrees of longitude oppose the some cover each hour?
15*
How is the length of twilight vary with change in latitude?
The higher the latitude, the longer the twilight periods will be. The further from the point where the suns noon rays are at 90* the longer the twilight period
