Navigation
Latitude & Longitude
Lesson 5.1
Sep 2012
Reference
From the Ground Up
Chapter 7.1:
Latitude & Longitude
Pages 177 - 179
Introduction
• The earth is an oblate spheroid that needs a
grid system to be navigable. Lines of latitude
and longitude are used to determine points on
the surface for navigation.
• Pilots need to know these systems in order to
fly from one point to another using various
navigation methods.
Outline
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Navigation Types
Latitude and Longitude
Co-ordinates
Time and Longitude
Great Circles and Rhumb Lines
Headings, Bearings, Tracks
One-in-Sixty
Navigation Types
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Pilotage
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Dead Reckoning
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Using self-contained airborne gyroscopic and electronic equipment to measure speed
and direction
Satellite Navigation
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Using radio aids
Inertial Navigation
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Using predetermined vectors and tracks
Radio Navigation
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Referencing only the ground and landmarks
Using satellites to triangulate position (GPS)
Celestial Navigation
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Measuring angles to heavenly bodies (sun, moon, stars)
Latitude
• Parallels of Latitude
– Circles whose plane lie parallel to equator
– Equator is great circle at 0°
– Parallels run 90° north and south of equator
Latitude
Longitude
• Meridians of Longitude
– Semi great circles joining true or magnetic poles
(true/magnetic meridians)
– Measured 0° to 180° east and west of prime
meridian (0°)
– International Date Line is 180°
Longitude
Co-ordinates
• Locations on Earth can be located by a
latitude and longitude intersection
• Example:
– Toronto, Canada = 43°39′N 79°23′W
– Sydney, Australia = 33°51′S 151°12′E
• Units:
– Degrees (°), Minutes (’), Seconds (”)
– 1° = 60’
– 1’ = 60”
Co-ordinates
Time and Longitude
•
Solar Day
– Interval between two successive transits of the sun
– Divided into 24 hours
– Sun travels 360° around earth, therefore 15° per hour
•
Conversions:
– 1 hour = 15 degrees longitude
– 1 min = 15 minutes longitude
– 1 sec = 15 seconds longitude
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360 degrees longitude = 24 hours
1 degree longitude = 4 min
1 minute longitude = 4 sec
1 second longitude = 1/15 sec
Coordinated Universal Time (UTC) is time at prime meridian. Also
known as Zulu (Z) time.
Time and Longitude
Great Circles
• Circle on Earth’s surface
whose plane passes through
the center of the earth (“cuts”
earth in half)
• Great Circle Route (or Arc) is
shortest distance between two
points
• Opposing meridians and
Equator are great circles
Rhumb Line
• Curved line on Earth’s
surface cutting all
meridians at the same
angle
• Parallels are rhumb lines
Headings and Bearings
• Directions measured degrees
clockwise from north
(0° or 360°)
• Heading
– Direction aircraft nose
(longitudinal axis) is pointing
– True heading uses true north
– Magnetic heading uses
magnetic north
Headings and Bearings
• Bearing (AKA Azimuth)
– Position of object relative to
your aircraft
– Measured clockwise from
longitudinal axis through
360°
– Not related to aircraft
heading
Tracks
• Track (AKA Intended Track or Required Track)
– Direction airplane intends to travel over ground
– Drawn on map as straight line from point A to point B
– Can be True, Magnetic or Compass Track
• Track Made Good
– Actual path traveled by airplane over ground
• Drift Angle
– Angle between airplane heading and track made good
– Expressed as degree left/right
Tracks
One-in-Sixty
• One-in-Sixty rule - An error in the track of
one degree will cause an error in position of
about one nautical mile in a distance of 60
nautical miles
8 NM
A
4 deg
60 NM
4 NM
60 NM
B
Next Lesson
5.2 – Navigation
Earth’s Magnetism
From the Ground Up
Chapter 7.2:
The Earth’s Magnetism
Pages 179 - 185