Maps And Charts Flashcards
What is a planar projection (plane)
Gnomonic
Polar stereographic production
Basically a piece of paper held up to the side of globe
What is a cylindrical projection
Wrap a piece of paper round the equator
= cylinder around globe
Mercator projection
Direct Mercator projection (when paper wrapped round equator)
Transverse Mercator = wrapper round a meridian = good for countries with lots of N/S and little E/W
What are the ideal properties of a chart
Distances should be shown at constant scale
Angles should be correctly shown
Also
Show a great circle as a straight line
Or
Show a thumb line as a straight line
Capable of producing chart anywhere in the world
Produce charts that line up when adjacent sections are fitted together
What is conformal / orthomorphic chart
Must be :
Scale is same in all directions
Projection must provide a right angle graticule
If orthomorphic = Angeles correctly represented
What is GRID MORA
Min off route altitude
Safety altitude
What happens to scale on a direct Mercator chart
As moving away from equator scale expands north south / east west
Not constant scale
Expands with the secant of 1/cos
Where is convergency correct on a direct Mercator chart
At equator
How does great circles get represented on a a direct Mercator chart
Concave to the parallel or origin
Where is scale perfect
Where scale is 99% correct
= 8°N / 8°S
= 480nm north and south
On a lamberts conformal projection what are parallels or latitude
Arcs of concentric circles
On a lamberts conformal projection what are meridians
Straight lines
Converting at the pole
Convergency is irrespective of latitude
On a simple conic convergence chart where does chart convergency equal earth convergency
Parallel of origin
What is a rhumb line on a simple conic chart
Curved line
Concave to the nearest pole
What is chart convergency = on a simple conic chart
Chlong x sin parallel of origin
What is the constant of the cone
Constant of the come = n = sin parallel origin = convergency factor
When is scale perfect on a simple conic lamberts projection
At the parallel of origin
What is a lamberts conformal projection
2 standard parallels
1 parallel or origin in between what
What is the constant cone of a lamberts conformal projection
Sin parallel of origin
Where is scale perfect on a lamberts conformal projection
Standard parallel
What is the scale perfection of the parallel or origin on the lamberts conformal projection
Max deviation of less than 1%
On a lamberts conformal projection what are rhumb lines
Concave to the nearest pole
What is the only true straight line on a lamberts conformal projection
Meridians
On a lamberts conformal projection where is chart convergency = earth convergency
Parallel or origin
North of parallel of origin = chart < earth
South of parallel of origin = chart > earth
Is there convergency for VOR on lamberts conformal projection
Nope
What is the current mapping system
WGS 84
What is the chart convergency on a polar stereographic
Change of longitude
Because sin Po = 1
Where is scale correct on a polar stereographic
Tangent of origin
How do great circles look on a polar stereographic
Practically = straight line
Reality = slight curve to tangent point
What are the only true straight lines on a polar stereographic
Meridians
Where is the light source placed for polar stereographic
Opposite pole to reduce scale expansion rate by half
What is the rate of expansion formula for polar stereographic projection
Secant ^2 Co-lat/2
What is chart convergency like at anywhere other than the pole for polar stereographic projection
Unless at pole
Chart convergence will be greater than earth convergence
What is the purpose of grid navigation
To overcome problems arising from constantly changing track angle on charts with converging meridians
What is grid convergence
Angular difference between grid north and true north
Grid convergency west true best
What is grivation / grid variation
The angle between grid and magnetic north is the sum of variation and grid convergence
What is Isogrivis
Lines of equal values of grivation
What is a standard gridded chart
Grid is aligned with prime meridian
On a standard gridded chart what is convergence
= longitude
East/ west = opposite of longitude
Therefor
80°E = a convergence of 80°W
“Convergence west, true best”
On the datum meridian for grid navigation what is the relationship between true and grid north
They are both the same
What is a position line (PL)
A line plotted from a beacon that you are on somewhere along
How do you get a fix from a beacon with position lines
Requires 2 position lines
Where is variation calculated for weather radar plotting
At aircraft
What track does a radio signal travel
Shortest distance between 2 points
= great circle track track
What is elevation
Vertical distance between mean sea level and ground / fixed object
What is height
Distance between aircraft and ground
What is pressure altitude
Altitude using 1013 as datum
What is flight level
Pressure altitude rounded to nearest 100ft
What is transition level
Higher than transition altitude
Lowest usable flight level above transition altitude
What is density altitude
Altitude adjusted for temperature change
