Definitions Flashcards
What kind of circle is a meridian line?
A semi great circle (half of a great circle) joined at the poles.
What is the prime meridian?
Runs through Greenwich England and is 0° and is the ‘starting point’ for all the other lines.
The International Date line is opposite the prime meridian at 180° and runs around continents for convenience (so these countries don’t have two days in one day). The IDL is where we decided that a ‘new day’ will ‘start’
Meridians of longitudes are divided into….
Degrees (60 min)
Minutes (60 seconds)
Seconds
These are not units of time, they are angular measurements.
For example: 15° = 1 hour.
The earth rotates 15° every hour
Meridians of longitude are measures east and west (not east TO west)
thats it
Lines of latitude
Also called parallels of latitude, are measured in chunks of 90° starting at the equator.
These ones are also expressed in degrees, minutes, and seconds
According to Harv’s Air, here is something that is very important to remember for the exam:
Unlike longitude, which has numbers we made up to fit with the rotation of the earth, what do latitude’s made up numbers represent that don’t have anything to do with the rotation of the earth?
1 hour = 1°
1 min = 1NM
60 seconds = 1 min (which equals 1NM, I guess)
How many feet is one nautical mile?
6080 feet (we picked this number because it divided equally into some other number we made up to measure how big around the earth is)
What two different kinds of lines is the equator?
Rhumb and Great Circle
What is the circumference of the equator? (This is very important information for a pilot to know. You will reference it daily. Possibly more)
24,000 miles
The tick marks for lines of latitude (these tick marks are displayed on the lines of longitude) on maps represent how many nautical miles across the ground?
1NM (6080ft)
**Lines of longitude do not have 1NM increments because as you get closer to the poles the lines get closer together. Lines of longitude can only be one NM apart at exactly the equator.
What is a great circle and a small circle?
Great Circles cut a globe/sphere in half to give two equal halves. It represents the shortest distance between two points
Small circle cuts it any way that doesn’t give two equal halves
A great circle is the shortest distance between two points, but what is the disadvantage of a great circle?
You can’t fly a constant heading. So you need to keep changing your heading as you fly
What is a rhumb line?
Lines that cut all meridians (lines of longitude) it passes through at the same angle
All lines of latitude are rhumb lines, including the equator (which is also a great circle)
What is better and worse about rhumb lines than great circles?
Following a rhumb line means you can keep a constant heading but it will be a greater distance
Are the lines on a VTA map rhumb lines or great circles?
Rhumb Lines
What is variation?
The difference in degrees between true north pole and the magnetic north pole.
How do you convert true to magnetic heading?
Apply the variation. East is least, west is best
What is an agonic line?
A line of zero magnetic variation (runs through thunder bay ish)
What is deviation?
The amount the compass is deflected by all the metal and electronics and crap in the plane. Will be on a little chart in the cockpit, add this to your MAGNETIC HEADING after you have corrected for variation
If you have multiple magnetic variations across your track, which one should you use for calculations?
Whichever is closest to the middle of your track
What is a bearing?
The location of an object or station relative to North
What is air position?
The position an aircraft or missile would have if there was no wind affecting it. Also known as no-wind position
What is one significant difference between lines of latitude and lines of longitude?
While lines of longitude converge at the poles, lines of latitude never converge. This is why lines of latitude are also called parallels of latitude.
This is why a one minute of latitude always equals 1NM, whereas a minute of longitude does not have a constant length.
Following a great circle route requires constant heading changes EXCEPT if:
That great circle is the prime meridian, in which case your flight is parallel with true north at all times and does not have any magnetic variation to correct for
