Nav Flashcards
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.
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.
Nautical mile conversions
=1.852km (happens to be the length of the runway condition that decides how wide the ATZ is) =6080ft
What is the definition of night?
Night is defined as the period from half an hour after sunset to half an hour before sunrise, sunset and sunrise being determined at surface level.
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 inter cardinal points?
Cardinal = north, east, south and west Inter cardinal 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 regards to charts what does conformal mean?
The preservation of angles required for navigation.
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.
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).
What is the heading of an aircrafts?
The direction, relative to north in which the aircraft is facing.
What is the track of an aircraft?
The path of the aircraft when the effect of the wind velocity is taken into account, e.g. A southerly wind will push the heading of an aircraft going west to the north.
