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Flashcards in Nav 01 Deck (115)
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What is UTC?

Universal Time Coordinated.

The longitudinal datum that assumes that the sun passes over at 1200 with a 24 hour clock.


What shape is the earth?

An oblate spheroid


Define a great circle.

A circle drawn on the surface of the earth whose radius and centre are the same as the earths. If used as a route will be the shortest route from a to b.


Define a small circle.

A circle drawn on the surface of the earth whose radius and centre are not the same as the earths.


What is the definition of the equator?

A great circle whose plane is perpendicular to the earths axis of rotation and which divides the earth into two equal hemispheres.


What is a meridian?

A semi great circle joining the poles.


What is a rhumb line?

A regularly curved line on the surface of the earth that cuts all meridians at the same angle. Appears curved on a Spherical representation of the earth (lamberts conic and globes) and straight on a flat one (mercator projection).


What is a nautical mile?

The length of arc of a great circle that sub tends an angle of one minute at the centre of the earth. 60nm in one degree as these are made out of minutes. 1nm= 1min.

40°x60 would equal 2400nm

40°and 20 minutes x60 would equal 2420nm


How far is a NM in KM?

=1.852km (happens to be the length of the runway condition that decides how wide the ATZ is)


What is the definition of night?


The period between the end of evening civil twilight and beginning of morning civil twilight. Civil twilight ends in the evening when the centre of the sun’s disc is 6 degrees below the horizon and begins in the morning when the centre of the sun’s disc is 6 degrees below the horizon.


What is are the datum reference points for lines of longitude and latitude?

The UTC prime meridian is the datum for longitude to 180west and east The equator is the datum for latitude up to 90 degrees either side at the poles


What are the figures for latitude and longitude?

Longitude is a seven digit number xxx degrees (60 mins) xx minutes (60 secs) xx seconds. E.g. 002 02 22. Latitude is a six digit number xx degrees (60 mins) xx minutes (60 secs) xx seconds. E.g. 51 02 22.


What are the cardinal and quadrantal points?

Cardinal = north, east, south and west

Quadrantal Points= NW, SE, SW, NE


Define grid north.

Grid north the direction of a grid line which is parallel to the central meridian.


Magnetic north

The direction indicated by a magnetic compass.


Define true north.

The direction of a meridian longitude which converges on the North Pole.


What is variation?

The angular difference between true north and magnetic north as measured by a magnetic compass at a particular location of the earth.


What is deviation?

The error induced in a compass by local magnetic fields.


How to convert from the different types of north.

West is best (+), east is least (-). True +/- variation = magnetic, +/- deviation = compass

I think of it as the north moving clockwise or anti-clockwise with the actual direction staying where it is. 



With regards to charts what does conformal mean?

The preservation of angles required for navigation. ie How accurately is portrays the thing it is representing.

So conformal means;

  • All angles and bearings on the earth are accurately represented
  • Scale distortion at any point must be the same in all directions
  • Each parallel must cross every meridian at right angles


What is a Mercator projection?

A cylindrical projection around the earth (can touch at the equator or any other point, transverse Mercator is one done horizontally). Most accurate at the point where it actually touches the earth, as you head away from this point the information becomes stretched and distorted.

On a Mercator; Rhumb lines are straight, Great circle routes are curved

They are conformal


What is a lambert conformal conic?

Refers to any projection in which meridians are mapped to equally spaced lines radiating out from the apex. Lines of latitude appear as arcs. Only accurate at the parallel of origin (point where it touches). This is the cone shaped one.

On a lambert conformal conic;

Rhumb lines appear as curved lines

Great circle routes are straight lines as the meridians are radiating out.

Is conformal, is nearly constant.


How is relief portrayed on a map?

Using contour lines and elevations (marking highest points), also achieved by hill shading (using colours to denote elevations).

Contour lines= Lines joining areas of equal elevation


What is the heading of an aircrafts?

The direction, relative to north in which the aircraft is facing.


What is a KM?


1/10,000th of the average distance between the equator and either pole.


How far is a NM in ft?



How far is a statue mile in  ft?



How far is 1 KM in ft?



What is the conversion factor from ft to m?



What is the conversion factor from m to ft?

x 3.2808