1 Basic Navigation principles 1 D.pptx

7/28/2019 1 Basic Navigation principles 1 D.pptx

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Basic Navigation principles

In the name of ALLAH, Most Gracious, Most Merciful

1Basic Comm/Navigation Developed for PIATraning Cneter by A/E Waqar Ahmad Khan


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Contents

1. What is Navigation?

2. The Terrestrial Coordinate System.

3. How to achieve a position fix?

4. Types of Bearings?

5. Heading.

6. Navigating.

7. RHO & Theta fixing.

8. Radio Navigation overview.

Basic Comm/Navigation Developed for PIATraning Cneter by A/E Waqar Ahmad Khan

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Navigation

Navisship

Agereto direct



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What is Navigation?

Navigation is the process of monitoring andcontrolling the movement of a craft or vehiclefrom one place to another.

It is also the term of art used for thespecialized knowledge used by navigators toperform navigation tasks.

All navigational techniques involve locatingthe navigator's position compared to knownlocations or patterns.



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The Globe

The Earth is NOT a perfect sphere. 7926.5 miles at its Equator.

79200 miles from North to South.

Lines of Longitude () Lines of longitude appear vertical with varying curvature in this projection, but are

actually halves of great ellipses, with identical radii at a given latitude.

Lines of Latitude (

) Lines of latitude appear horizontal with varying curvature in this projection; but

are actually circular with different radii. All locations with a given latitude arecollectively referred to as a circle of latitude.

The Equator: The equator divides the planet into a Northern Hemisphere and a Southern

Hemisphere, and has a latitude of 0

The Mercator Projection



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Great Circles The largest circle that can be drawnon the surface of the earth & all like it.

Equator

Meridians

Equator Meridian Great Circle

Terrestrial Coordinate System



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Lines of Longitude

Longitude

The demarcation of the longitude coordinate is done with lines going up and down are

called the meridians. A figure to the right shows a few meridians. Longitude ranges from 0

to 180 East and 0 to 180 West.The longitude angle is measured from the center of the earth as shown in the earth graphic

to the right.

The zero point of longitude is defined as a point in Greenwich, England called the Prime

Meridian.

http://astro.unl.edu/naap/motion1/tc_units.htmlhttp://astro.unl.edu/naap/motion1/tc_units.html


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Why Greenwich of all places?

Prior to 1884 there were several landmarks from whichlongitude was measured. Unlike the measurement of latitude,longitude was very difficult to measure while navigating. Errorswere made, sometimes with tragic results. In response to onesuch tragic result England passed the Longitude Act a contestfor a practicable method of determining longitude at sea with ahefty cash reward. John Harrison is credited by history as beingthe person to do so with his inventions of very precise

chronometers that weren't based on pendulums (pendulumsdon't keep good time at sea). The story, however, is aremarkable one of prejudice, politics, and science. Harrison wasnever awarded the prize by the Board of Longitude set up bythe act only through direct intervention from parliament washe awarded money for his efforts.

In 1884, U.S. President Arthur organized the InternationalMeridian Conference, attended by delegates from 25 nations.Partly because of John Harrison being the first to come up witha practicable method of determining longitude at sea, over twothirds of sea freighters used Greenwich as the reference pointfor longitude. This carried over to a vote by the conferenceestablishing Greenwich as the reference point of 0 longitude.



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Lines of Latitude



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Lines of Latitude

Latitude The demarcation of the latitude

coordinate is done with circles onthe globe parallel to the equator.

These parallel circles, fittinglyenough, are calledparallels oflatitude. The figure to the rightshows several parallels of latitude.

Latitude goes for 0 at the equatorto +90 N at the North Pole or -90 Sat the South Pole where the angle is

also measured from the center ofthe earth as shown in the earthgraphic to the right.



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Assessment

What is the value of latitude that the North

pole and the South pole lie on?

What is the maximum angular difference

between two points on the globe with respect

to longitude?



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How to locate any point



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Great Circles The largest circle that can be drawnon the surface of the earth & all like it.

Equator

Meridians

Equator Meridian Great Circle

Great Circles



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The Great Circles

A great circle, also known as an orthodrome or Riemannian circle, of

a sphere is the intersection of the sphere and a plane which passesthrough the center point of the sphere, as opposed to a general circleof a sphere where the plane is not required to pass through thecenter.

Any diameter of any great circle coincides with a diameter of thesphere, and therefore all great circles have the same circumference as

each other, and have the same center as the sphere. A great circle isthe largest circle that can be drawn on any given sphere.

The minor arc of a great circle between two points is the shortestsurface-path between them. In this sense the minor arc is analogousto straight lines in spherical geometry. The length of the minor arcof a great circle is taken as the distance between two points on a

surface of a sphere, namely the great-circle distance



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The Nautical Mile

The nautical mile (symbol M, NM or nmi) isa unit of length that is about one minute ofarc of latitude along any meridian, or about one minute ofarc of longitude at the equator. By international agreementit is exactly 1,852 meters (approximately 6,076 feet).

The nautical mile remains in use by sea and air navigatorsworldwide because of its convenience when working withcharts.

Most nautical charts are constructed on the Mercatorprojection whose scale varies by approximately a factor ofsix from the equator to 80 north or south latitude. It is,therefore, impossible to show a single linear scale for useon charts on scales smaller than about 1/80,000.

The nautical mile circumvents this problem by being equalto a minute of latitude on a chart, which allows anydistance measured with a chart divider to be simply

converted using the chart's latitude scale.

Historical definition - 1 nautical mile

Visual comparison of a kilometre, statute mile, and nautical

mile



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Nautical Mile per Hour-KNOT

The knot (pronounced not) is a unit of speed equal toone nautical mile (which is defined as 1.852 km) per hour,approximately 1.151 mph.[

The knot is a non-SI unit accepted for use withthe International System of Units (SI).Worldwide, the knotis used in meteorology, and in maritime andair navigationfor example, a vessel travelling at 1 knotalong a meridian travels one minute ofgeographic latitude in one hour.

Etymologically, the term knot derives from counting thenumber of knots in the line that unspooled from the reel ofa chip log in a specific time.

1 KNOT = 6080 / 5280 = 76/66 m.p.h

http://en.wikipedia.org/wiki/Knot_(unit)http://en.wikipedia.org/wiki/Knot_(unit)


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Activity



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Solution



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Getting a position fix

Position fixing

is the branch of navigation concerned with the use ofa variety of visual and electronic methods todetermine the position of a ship, aircraft or person onthe surface of the Earth.

These techniques include:

Position lines and position circles

Celestial navigation Radio navigation

Satellite navigation system



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Using Celestial Objects

Using the sextant

and, the lines of

latitude and the

celestial objectslike the Sun or the

Polar Star one can

position oneselfw.r.t. latitude.



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Activity



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Solution



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Using magnets for getting a fix

Magnetic properties of materials used for ages

for finding headings.

The synonym for the compass is the

Lodestone which means Leading stone.

Natural magnets have now been substituted

by artificial means which are mush more

sensitive.



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Magnetic Variation

The difference between the true North and the Magnetic North.

Isogonal Lines = Lines drawn on the charts connecting points ofequal variation.



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How do we get there?

Plot a course

Whats a course?

path of intended motion

Steer a heading

Whats a heading?

the direction the aircraft is pointed

Make a good track

Whats a track?

the aircrafts path over the ground



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Course, Heading, & Track

Big Bad Wind

Basic Comm/Navigation Developed for PIATraning Cneter by A/E Waqar Ahmad Khan

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Bearings

a bearing is the actual (corrected) compass direction of the forward course of the aircraft.

A true bearing is measured in relation to the fixed horizontal reference plane of truenorth, that is, using the direction toward the geographic north pole as a reference point.

A magnetic bearing is measured in relation to magnetic north, that is, using the directiontoward the magnetic north pole as a reference.

A grid bearing is measured in relation to the fixed horizontal reference plane of grid

north, that is, using the direction northwards along the grid lines of the map projection asa reference point.

A compass bearing, as in vehicle or marine navigation, is measured in relation tothe magnetic compass of the navigator's vehicle or vessel. It should be very close to themagnetic bearing. The difference between a magnetic bearing and a compass bearing isthe deviation caused to the compass by ferrous metals and local magnetic fieldsgenerated by any variety of vehicle or shipboard sources (steel vehicle bodies/frames or

vessel hulls, ignition systems, etc.) A relative bearing is one in which the reference direction is straight ahead, where the

bearing is measured relative to the direction the navigator is facing (on land) or in relationto the vessel's bow (aboard ship).



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The Compass Card


True & magnetic courses are given in 3 digits, e.g.

090 Relative bearings are given in degrees or clock

position, e.g. 10 left of the nose, or 11 oclock


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Assessment



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Answers



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True Bearing

A true bearing is measured in relationto the fixed horizontal reference plane

of true north, that is, using the

direction toward the geographic north

pole as a reference point.



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Magnetic Bearings

A magnetic bearing ismeasured in relationto magnetic north, that is, using

the direction towardthe magnetic north pole as areference.

Westerly variations- Magnetic

Bearing > True Bearing. Easterly variations- Magnetic

Bearing < True Bearing.



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Deviation

In nautical terminology deviation is the magnetic compass error caused by

magnetized iron within the structure of the aircraft. Any magnet, in the proximity of a compass, will cause the compass needle to

"deviate" from Magnetic North. In the case of big steel or iron structures, suchas aircraft, this deviation error can be both large and variable.

The problem of analyzing and correcting the magnetic deviation error is complex- because the magnetized iron in every aircraft is a combination of iron particles

which have become 'permanently' magnetized and iron particles which containsome "temporary" magnetism that has been induced by the Earth's magneticfield.

Deviation errors vary with the ship's magnetic heading (the angle the shipmakes to magnetic north).

Magnetic declination, also called variation, is the angular difference between

true north and the direction of the Earth's magnetic field at any point on theEarth's surface.

The corresponding definition, for deviation, is the angular difference betweenmagnetic north and the compass needle. Variation and deviation both influencemagnetic compass needles. Their combined effect is known as magnetic"Compass error"



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Compass Bearing



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Activity



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Relative Bearing



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Aircraft Heading



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Getting from one point to another



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Solution



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Great Circles & Rhumb Lines

The shortest path from onepoint to the other on the globe is

on a great circle. But it is more feasible to follow a

route of constant heading whichlies on a Rhumb Line.

The Mercator Projection



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This the shortest way between two

points on the Earth is a.?


Area Navigation


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Area Navigation

The compromise between travelling a great circle and a

Rhumb Line-Follow way points. Tries to minimize the route deviation from a great circle and

at the same time minimizes the load on the pilot withrespect to changes of headings.



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Rho and Theta Fixing



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Bearing & Distance fixing




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Radio Navigation

ADF.

VOR.

GPS.

OMEGA.

ILS.



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Automatic Direction Finding



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Activity


Solution


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Solution



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Very High Frequency Omni Ranging



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Co Located VOR-DME Station



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Hyperbolic Navigation



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Self Assessment

55Basic Comm/Navigation Developed for PIA

Traning Cneter by A/E Waqar Ahmad Khan


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Solution

56Basic Comm/Navigation Developed for PIA

Traning Cneter by A/E Waqar Ahmad Khan

Th R di N i ti S t


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The Radio Navigation Systems

Basic Comm/Navigation Developed for PIA

Traning Cneter by A/E Waqar Ahmad Khan 57

Basic Navigation Parameters


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Basic Navigation Parameters

Basic Comm/Navigation Developed for PIA

Traning Cneter by A/E Waqar Ahmad Khan 58


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Feedback

What is navigation?

Why is the Earth divided into Lines ofLongitude and Latitude?

If we want to fly the shortest route from onepoint to another on the Earth then do wefollow a Rhumb Line or a Great Circle? Why?

How does an aircraft practically fly from onepoint to another using modern navigationaids?

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