Sep 2012Lesson 5.1

Navigation

Latitude & Longitude

Reference

From the Ground UpChapter 7.1:Latitude & LongitudePages 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• Navigation Types• Latitude and Longitude• Co-ordinates• Time and Longitude• Great Circles and Rhumb Lines• Headings, Bearings, Tracks• One-in-Sixty

Navigation Types• Pilotage

– Referencing only the ground and landmarks

• Dead Reckoning– Using predetermined vectors and tracks

• Radio Navigation– Using radio aids

• Inertial Navigation– Using self-contained airborne gyroscopic and electronic equipment to measure speed

and direction

• Satellite Navigation– Using satellites to triangulate position (GPS)

• Celestial Navigation– 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

– 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

A B60 NM 60 NM4 deg 4 NM

8 NM

Next Lesson

5.2 – NavigationEarth’s Magnetism

From the Ground UpChapter 7.2:The Earth’s MagnetismPages 179 - 185