Latitude, Longitude, Earth's Magnetism & Compass Errors 4 . 2 Latitude, Longitude, Earth's Magnetism & Compass Errors

Meridians of Longitude and Parallels of Latitude circles on the earth’s surface whose planes lie parallel to the equator equator is a great circle on the surface of the earth lying equidistant from the poles measured from 0° to 90° north and south of equator measured in degrees (°), minutes (’) and seconds (”) semi great circles joining the true or geographic poles of the earth (true meridians) measured from 0° to 180° east and west of prime meridian 180th meridian is called the International Date Line measured in degrees (°), minutes (’) and seconds (”) Note: there are 60 minutes in a degree and 60 seconds in a minute

Determining Geographical Coordinates Intersection of the lines of latitude and longitude marking a position on a map used to locate a fixed object on the earth’s surface change of latitude and the change of longitude between two places relate one position on the surface with another

Time and Longitude Solar Day - interval between two successive transits of the sun. It is divided into 24 hours. The sun travels around the earth once every day. It travels 360 degrees of longitude in one day. Time can therefore be expressed in terms of longitude: 24 hours - 360 degrees longitude 1 hour - 15 degrees longitude 1 min - 15 minutes longitude 1 sec - 15 seconds longitude

Time and Longitude cont’d 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) Used so that a universal standard time exists for reference at any point on the earth based upon measurements of time in a number of places on the earth. It is also referred to as Z or zulu time. UTC replaced Greenwich mean time (GMT), which was once the universally accepted standard. UTC is the local mean time for the prime meridian. Winter time is the same as Standard Time.

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Navigation Latitude, Longitude, Earth’s Magnetism, and Compass Errors Let's try a few review questions on Navigation: Question #1 - Name a semi great circle joining the true poles of the earth. A Meridians of longitude B Parallels of latitude C Meridians of latitude D Parallels of longitude

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Navigation Latitude, Longitude, Earth’s Magnetism, and Compass Errors Let's try a few review questions on Navigation: Question #2 - What is the length of 15° longitude? A 24 hours B 1 hour C 1 minute D 1 second

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Magnetism True North is the north pole of the earth. Magnetic North is the direction the compass needle lies without considering deviation. Magnetic north is not a fixed position. The magnetic field of the earth changes as magnetic north moves about in a circle.

Magnetic Variation Defined as the angle between the true meridian and magnetic meridian in which the compass needle lies. It is also known as magnetic declination in other disciplines.

Converting between True and Magnetic Heading To convert from True to Magnetic Heading: Add Westerly Variation Subtract Easterly Variation Example: True Heading: 320° Variation: 6° West Find Magnetic Heading. 320° + 6° = 326°

To convert from Magnetic to True Heading: Add Easterly Variation Subtract Westerly Variation Example: Magnetic Heading: 256° Variation: 3° West Find True Heading 256° - 3° = 253°

Helpful Reminder East is Least West is Best

Compass Deviation The angle between the magnetic heading and the compass heading. Compass heading is magnetic heading corrected for deviation.

Converting between Magnetic and Compass Heading To convert from Magnetic to Compass: Add Westerly Deviation Subtract Easterly Deviation Example: Magnetic Heading: 050° Deviation: 2° West Find Compass Heading. 050° + 2° = 052°

To convert from Compass to Magnetic Add Easterly Deviation Subtract Westerly Deviation Example: Compass Heading: 201° Deviation: 1° West Find Magnetic Heading. 201° - 1° = 200°

All variation and deviation can be remembered by: T - True Track V - Variation M - Magnetic Heading D - Deviation C - Compass Heading

NOTE: You must use the buttons in the Confirmation Stage

Navigation Latitude, Longitude, Earth’s Magnetism, and Compass Errors Let's try a few review questions on Navigation: Question #3 - What is the angle between the true meridian and the magnetic meridian? A Magnetic heading B Compass heading C Variation D Deviation

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Navigation Latitude, Longitude, Earth’s Magnetism, and Compass Errors Let's try a few review questions on Navigation: Question #4 - If your aircraft has a true heading of 240° and there is a variation of 20° West, what is the magnetic heading? A 220° B 260° C 240° D 250°

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Compass Errors A compass has several errors which may lead it to not point directly to magnetic north. Knowledge of their presence will assist the pilot in correcting for them.

Magnetic Dip The earth’s lines of force are horizontal at the equator but become vertical towards the poles. Causes the compass to tend to dip in higher latitudes.

Northerly Turning Error The compass will misread when the aircraft is in a banked attitude and turning. Error is most apparent on headings of north and south and is greatest over the poles. Always make sure the wings are level while reading the compass on north or south headings.

On turns from the north, northerly turning error causes the compass to lag. On turns from the south, northerly turning error causes the compass to lead.

Acceleration Error On east and west headings, acceleration causes a turning moment, tending to rotate the magnet system and so causing deflection of the compass card. When the airplane decelerates, a similar effect is seen but the deflection will be in the opposite direction. The effect of acceleration and deceleration compass errors is nil on north and south headings. When reading the compass on east or west headings, always make sure that airspeed is constant.

While flying an east/west heading, acceleration causes the compass to register a turn to the north. While flying an east/west heading, deceleration causes the compass to register a turn to the south.

NOTE: You must use the buttons in the Confirmation Stage

Navigation Latitude, Longitude, Earth’s Magnetism, and Compass Errors Let's try a few review questions on Navigation: Question #5 - The error on turns from north where the compass lags is known as . A Magnetic dip B Acceleration and deceleration error C Northerly turning error D Easterly and westerly error

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Navigation Latitude, Longitude, Earth’s Magnetism, and Compass Errors Let's try a few review questions on Navigation: Question #6 - The compass needle dips toward the surface of the earth at the poles. What is this error called? A Magnetic dip B Acceleration and deceleration error C Northerly turning error D Easterly and westerly error

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Navigation Latitude, Longitude, Earth’s Magnetism, and Compass Errors Congratulations!! You have now completed the Latitude, Longitude, Earth’s Magnetism, and Compass Errors lesson of the Navigation Module. Of course, this lesson is always available to you for future reference if required. You are now ready to move along to the next Navigation lesson you have not completed or to any other module you wish. You can advance to the Self Test Module if you feel ready to challenge the final exam. Good Luck!