Podcast
Questions and Answers
What is the angle between the true great-circle track and the true rhumb-line track at point A (60° S 165° W) and B (60° S 177° E)?
What is the angle between the true great-circle track and the true rhumb-line track at point A (60° S 165° W) and B (60° S 177° E)?
What is the convergency between points A (50N 10W) and B (58N 02E)?
What is the convergency between points A (50N 10W) and B (58N 02E)?
Which statement correctly describes the convergency of meridians?
Which statement correctly describes the convergency of meridians?
What is the convergency at 50° N between the meridians 105° W and 145° W?
What is the convergency at 50° N between the meridians 105° W and 145° W?
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A great circle track joins position A (59° S 141° W) and B (61° S 148° W). What is the difference between the great circle
track at A and B?
A great circle track joins position A (59° S 141° W) and B (61° S 148° W). What is the difference between the great circle track at A and B?
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What is the standard formula for calculating convergency?
What is the standard formula for calculating convergency?
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Which line generally lies closer to the pole?
Which line generally lies closer to the pole?
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At which latitude is the value of convergency half the value at 60° N?
At which latitude is the value of convergency half the value at 60° N?
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What is the final position of an aircraft that flies 600 NM South, then 600 NM East, then 600 NM North, and finally 600 NM West from position 04° 00N 030° 00W?
What is the final position of an aircraft that flies 600 NM South, then 600 NM East, then 600 NM North, and finally 600 NM West from position 04° 00N 030° 00W?
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Which statement about meridians is true?
Which statement about meridians is true?
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In the context of course conversion, if conversion angle is referred to as 'convergency', what does this signify?
In the context of course conversion, if conversion angle is referred to as 'convergency', what does this signify?
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What type of route is necessary to fly from position A (10° 00N, 030° 00W) to position B (30° 00N, 050° 00W) while maintaining a constant true course?
What type of route is necessary to fly from position A (10° 00N, 030° 00W) to position B (30° 00N, 050° 00W) while maintaining a constant true course?
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If the initial great circle direction from 45° N 14° 12W to 45° N 12° 48E is to be determined, which option is correct?
If the initial great circle direction from 45° N 14° 12W to 45° N 12° 48E is to be determined, which option is correct?
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What is the rhumb line track P - Q when the great circle from P to Q is measured at P=095° in the Southern Hemisphere with a conversion angle of 7°?
What is the rhumb line track P - Q when the great circle from P to Q is measured at P=095° in the Southern Hemisphere with a conversion angle of 7°?
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What is the approximate initial great circle track from A (S 27° 30 E 017° 45) to B (S 27° 30 E 029° 15)?
What is the approximate initial great circle track from A (S 27° 30 E 017° 45) to B (S 27° 30 E 029° 15)?
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Given two meridians at latitude 60º that are 40º apart, what is the calculated convergence?
Given two meridians at latitude 60º that are 40º apart, what is the calculated convergence?
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You are flying from A (50N 10W) to B (58N 02E). What is the Convergency between A and B?
You are flying from A (50N 10W) to B (58N 02E). What is the Convergency between A and B?
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The shortest distance between 2 point of the surface of the earth is:
The shortest distance between 2 point of the surface of the earth is:
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Study Notes
Great Circle and Rhumb Line Tracks
- Great Circle Track: The shortest distance between two points on the Earth's surface, following a curve along the sphere's surface.
- Rhumb Line Track: A line of constant true bearing, cutting meridians at a constant angle.
- Convergency: The angular difference between meridians at a given latitude, crucial for navigation; greater using rhumb lines than great circles.
- Formula for Convergency: Convergency = dlong * cos(mean latitude), where dlong is the difference in longitude between the two meridians and mean latitude is the average of latitudes.
- Shortest Distance: A great circle track is the shortest distance between two points on the Earth's surface.
- Latitude Difference: Calculated by subtracting the smaller latitude from the larger latitude.
Convergency Calculations
- Convergency Example: At 50°N latitude, the convergency between 10°W and 14°W meridians is approximately 30.6°. This is crucial for navigation.
- Relationship between Track and Convergency: The turning rate of a great circle track from one point to another changes as a function of convergency and latitude.
Positional Considerations
- Positional Changes: The great circle track from one position to another may change more in magnitude (increase or decrease) depending on latitude. This is an important concept in navigation; for example, the great circle track at A may increase by 3 degrees compared to the one at B.
- Turning Angle: The turning angle differs between great circle and rhumb line paths.
Earth's Shape
- Earth's Shape: The Earth is an oblate spheroid, slightly flattened at the poles and bulging at the equator.
- Equatorial Diameter: The equatorial diameter is greater than the polar diameter.
Rhumb Line Track and Great Circle Track
- Conversion angle: The conversion angle accounts for the fact that true course may be different in relation to the rhumb line or great circle tracks. Note: conversion angle = 0.5 convergency.
- Maintaining Constant True Course: To maintain a constant true course, a rhumb line must be followed. A great circle track will result in varying true courses.
- Rhumb Line and Final Position: An aircraft following a series of rhumb line segments will return to its initial position; if a great circle track is followed, it will not.
Meridians
- Direction of Meridians: Meridians run north-south (true direction) on both hemispheres.
- Constant Distance Between Meridians: The distance between meridians varies with latitude—greater at the equator, smaller at the poles.
Great Circle Track Calculations
- Calculating Initial Great Circle Track: Methods for determining the initial great circle track are important for accurate navigation, such as using formulas or tools.
- Example: Initial Great Circle Track: An example illustrating determination of the initial great-circle track between specific locations at latitude and longitude, considering both the northern and southern hemispheres. This process is crucial for accurate navigation.
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Description
Explore the concepts of great circle and rhumb line tracks in navigation. Understand their significance, the formulas used for convergency calculations, and how they relate to the shortest distances on Earth's surface. This quiz is essential for anyone looking to enhance their navigation skills.
