Aircraft Navigation- INS / GPS

1
Shanks
Inertial Navigation
&
Global Positioning System
Inertial Navigation
&
By Shankar NarayanBy Shankar Narayan
1
Aircraft Navigation
Inertial Navigation
&
Inertial Navigation
&
Flow of presentation
11 What is Navigation
22 Inertial Navigation System Concepts
33 The Ring Laser Gyro
44 GPS Concepts & Introduction to GPS
55 How GPS Works?

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29th August 2009
NavigationNavigation
Navigation is the art of guiding oneself to one’s
desired Destination
For Navigation You need to Know your position
at any instant of time!
3Shanks
Shanks
January 23, 2017
Inertial Navigation SystemInertial Navigation System
Presented by
Shankar Narayan
INS conceptsINS concepts

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January 23, 2017
What is an Inertial Navigation System
(INS)?
• Every object that is free to move in space has six
"degrees of freedom" - or ways it can move.
• There are three linear degrees of freedom (x,y,z) that
specify your position and three rotational degrees of
freedom (theta (pitch), psi (yaw), and phi (roll)) that
specify your attitude.
• If you know these six variables, you know where you are
and which way you're pointed
Inertia – inertness, property by which matter continues in existing state of rest
Or uniform motion, unless acted on by external force
Attitude
• Yaw
• Roll
• Pitch

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January 23, 2017
•
The six parameters of freedom
A body's actual spatial behavior / movement can be
described with three translatory and three rotary
components.
• : three translatory (x-, y-, z-acceleration) and three rotatory
components (x-, y-, z-angular velocity)
January 23, 2017
Inertial Navigation is accomplished by
integrating the output of a set of sensors
to compute position, velocity, and attitude.
The sensors used are:
1. Gyros
2. Accelerometers.
Inertial NavigationInertial Navigation

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INS
• The present Inertial Navigation uses 'solid state' systems
consists of expensive laser-gyros and integrated sensor
devices (accelerometers) in MEMS technology (Micro
Electro-Mechanical System).
• Inertial navigation systems (INS) are used in civil and
military aviation, cruise missiles, submarines and space
technology.
January 23, 2017
What is inertial Measurement Unit?
• An inertial measurement unit, or IMU, is a "clump" of six
inertial sensors. Three linear accelerometers and three
rate gyros make up our IMU. Usually, an IMU also
contains a computational unit to do the position
calculations based off of the sensors

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January 23, 2017
LASER
GENERAL INFORMATION
January 23, 2017
LASER
• LIGHT
• AMPLIFICATION BY
• STIMULATED
• EMISSION OF
• RADIATION
STIMULATE = EXITE
• LASER IS A COHERENT SOURCE OF LIGHT
• LASER LIGHT IS MORE DIRECTIONAL, MORE MONOCHROMATIC &
HENCE MORE BRIGHT COMPARED WITH OTHER SOURCES OF
LIGHT.
MONOCHROMATIC = SINGLE WAVE LENGTH/COLOR
COHERENT = COSTANT PHASE/CONSISTANT
Spontaneous = occurring without any external cause

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January 23, 2017
LASER
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January 23, 2017
RING LASER GYROMETER

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January 23, 2017
RLG PRINCIPLE
January 23, 2017
LASER GYRO

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RLG Block Triangle

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mirror
mirror mirror
mirror
mirror
mirror
ROLL
HEADING (YAW)
PITCH

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RLG PRINCIPLE
January 23, 2017
ADDING OF LASER BEAMS
PRODUCE FRINGES

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January 23, 2017
MOTION DETECTION
• WHEN NO MOVEMENT – FRINGE PATTERN IS
FIXED.
• WHEN A MOVEMENT IS DETECTED – THE FRINGE
PATTERN MOVES, DEPENDS UPON THE DIRECTION
OF MOTION OF THE GYRO & IS PROPORTIONAL TO
THE RATE OF ROTATION.
January 23, 2017
LASER IN RLG
• TYPE OF LASER USED IS HELIUM / NEON. HENCE
THE COLOUR IS REDDISH ORANGE.
• FREQUENCY FOR LASER = 1000000000000000
CYCLES PER SECOND.
• THE GLASS TUBE IS MADE OF ‘ZERO DUR’ GERMAN
GLASS INCLUDING THE MIRRORS.

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January 23, 2017
ACCELERO METERSACCELERO METERS
January 23, 2017
The apparatus to measure
acceleration uses the property of
each physical body to persist in a
state of rest on uniform motion.
This property is called inertia and is
characterised by a force F which,
under acceleration g, moves the
mass in the opposite direction to the
acceleration.
AccelerometerAccelerometer
0 1 2
Mass
0 1 2
Mass
Deflection with 1
unit of acceleration
0 1 2
Mass
Deflection with 2
units of acceleration
F = m γ

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January 23, 2017
The measurement instruments are
called accelerometers and may be
either linear or pendular, this later type
at present being the most widely used.
Under the effect of an acceleration g
of 20 m/s2, the mass moves along
measurement axis. The marked
graduations allowed the value of the
acceleration to be obtained that is 20
m/s2.
20 0 -20
Measurement
axis
γγγγ = 20 m/s²
LINEAR ACCELEROMETER
(principle)
20 0
Measurement
axis
-20
PENDULAR ACCELEROMETER
(principle)
January 23, 2017
In the case of a pendulum accelerometer,the influence of the earth gravity takes
action as soon as the pendulum leaves its point of equilibrium even if the sensitive
axis is perpendicular to the force of attraction g.
The accelerometer measurement is then erroneous. In order to cancel out this
influence the pendulum must be made to work around its point of equilibrium.
γγγγ = 20 m/s²
0
Sensitive
axis
PENDULAR ACCELEROMETER
g
γγγγ
g

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January 23, 2017
January 23, 2017
• Accelerometer Used Is Pendulum Type Accelerometer.
• Displacement Of The Pendulum Depends On
Acceleration.
• From The Displacement Value Of The Pendulum,
Acceleration Can Be Computed.

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January 23, 2017
ACCELEROMETER PRINCIPLE
FLEXIBL
E SHADE
MAGNETIC
DEVICE
DETECTORS
COILS
PENULUM
WITH HINGE
January 23, 2017
ACCELEROMETER OPERATION
With No Motion, Pendulum Is Centered, And The
Capacitor Bridge Is Balanced
When A Motion Is Detected,the Pendulum Is Displaced
And The Bridge Is No Longer Balanced. So A Current Is
Induced Proportional To The Displacement Of The
Pendulum
Pendulum Is Bought Back To Its Null Point By Means Of
A Mechanism Which Generates A Field In Opposition To
The Pendulum Movement.
The Value Of The Current Necessary For The
Mechanism To Keep The Pendulum At Zero Represents
The Measured Acceleration

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GLOBAL POSITIONING SYSTEMGLOBAL POSITIONING SYSTEM
.. In everyday life
Presented by Shankar Narayan
GPSGPSConceptsConcepts
Position of any point on earthPosition of any point on earth
Any location on Earth is described
by three numbers--its latitude
its longitude and its altitude.
If a pilot or a ship's captain
wants to specify position
on a map, these are
the "coordinates" they would use.
Any location on Earth is described
by three numbers--its latitude
its longitude and its altitude.
If a pilot or a ship's captain
wants to specify position
on a map, these are
the "coordinates" they would use.
Position
LatitudeLatitude LongitudeLongitude AltitudeAltitude
Geographical
Coordinates &
Altitude
Geographical
Coordinates &
Altitude
*

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LatitudeLatitude
• On a globe of the Earth, lines
of latitude are circles of
different size. The longest is
the equator, whose latitude is
zero, while at the poles--at
latitudes 90° north and 90°
south (or -90°) the circles
shrink to a point.
To specify the latitude of some
point P on the surface, draw
the radius OP to that point.
Then the elevation angle of
that point above the equator
is its latitude λ--northern
latitude if north of the equator,
southern (or negative) latitude
if south of it.
LongitudeLongitude
• On the globe, lines of constant
longitude ("meridians") extend
from pole to pole, like the
segment boundaries on a
peeled orange.
• For historical reasons, the
meridian passing the old Royal
Astronomical Observatory in
Greenwich, England, is the
one chosen as zero longitude

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29th August 2009
Latitude/ Longitude & DirectionsLatitude/ Longitude & Directions
Radius of Earth = 6 378.1 kilometersRadius of Earth = 6 378.1 kilometers
3737ShanksShanks Training & Development Institute, HAL, NasikTraining & Development Institute, HAL, Nasik
*
29th August 2009
latitude
l
o
n
g
i
t
u
d
e
20 degree
73
de
gr
ee
73deg. 54 min 52 sec
ojhar
20 deg. O7 min 22 sec
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38

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The Longitude ( Meridian)The Longitude ( Meridian)
• A lines of longitude is also called a meridian, derived from the Latin,
from meri, a variation of "medius" which denotes "middle", and
diem, meaning "day." The word once meant "noon", and times of
the day before noon were known as "ante meridian", while times
after it were "post meridian." Today's abbreviations a.m. and p.m.
come from these terms, and the Sun at noon was said to be
"passing meridian". All points on the same line of longitude
experienced noon (and any other hour) at the same time and were
therefore said to be on the same "meridian line", which became
"meridian" for short.
• Longitudes are measured from zero to 180° east and 180° west
(or -180°), and both 180-degree longitudes share the same line,
in the middle of the Pacific Ocean
Local & Universal TimeLocal & Universal Time
• Local time is actually a measure of the position of the Sun relative
to a locality. At 12 noon local time the Sun passes to the south and
is furthest from the horizon (northern hemisphere). Somewhere
around 6 am it rises, and around 6 pm it sets. Local time is what you
and I use to regulate our lives locally, our work times, meals and
sleep-times.
• universal time (UT), which can be defined (with some slight
imprecision, no concern here) as the local time in Greenwich,
England, at the zero meridian. That is, a single agreed-on clock,
marking time world-wide, not tied to our locality. Astronomers,
astronauts and people dealing with satellite data may need a time
schedule which is the same everywhere, not tied to a locality or time
zone. The Greenwich mean time, the astronomical time at
Greenwich (averaged over the year) is generally used here. It is
sometimes called Universal Time (UT).

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International Date LineInternational Date Line
• International date line has been established--most of it
following the 180th meridian--where by common
agreement, whenever we cross it the date advances one
day (going west) or goes back one day (going east).
That line passes the Bering Strait between Alaska and
Siberia, which thus have different dates, but for most of
its course it runs in mid-ocean and does not
inconvenience any local time keeping.
What is GPS ?
(GPS) is a satellite
Navigation System
which is invented
and Controlled
by the US
Department
of Defense (DOD)
(GPS) is a satellite
Navigation System
which is invented
and Controlled
by the US
Department
of Defense (DOD)

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Global positioning systemGlobal positioning system
• GPS provides specially coded satellite signals.
• These Signals can be processed in a GPS
Receiver.
• The Receiver after processing, outputs highly
accurate - position , velocity, time and altitude
information, to the GPS users around the world.
GPS Uses in Everyday lifeGPS Uses in Everyday life
• Developed for military use( ships, aircrafts..)
• Use in tunnel construction –English # French
• Used in cars, Buses, Trains, to monitor Position
• Help save life- Use in emergency Vehicles
• Moving Map displays in vehicles Guided by GPS
• Used in Surveying, Wildlife management.
• GPS equipped Balloons used to find explore the ozone
layer.
• Explorers use GPS extensively
*

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GPS Systems of the World
• GLONASS ( Russian) – To be completed by 2010
Global Navigation Satellite System
• NAVSTAR ( American)- Completed
Navigation System by Timing and Ranging
• GALILEO (England) – To be completed by 2020
*
The program was created by the US Department of
defense (DOD) in 1973.
The First GPS satellite, Block I developmental
model was launched in February 1978.
For Global operation of GPS System, a
constellation of 24 satellites (Minimum) is required
Birth of NAVSTAR GPS
*

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The 24 satellites constellation mile stone was achieved
in June 1993
The system gained fame ‘desert storm’ by providing
unprecedented navigational accuracy for allied air and
ground forces.
Global positioning systemGlobal positioning system
‘The Global Positioning System Fully
Operational, This declaration came from US
Air force on July 17th 1995.
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The Three
Segments
of GPS
The Three
Segments
of GPS
GPSGPS
4848

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GPS consists of Three SegmentsGPS consists of Three Segments
Control
segment
Control
segment
consists of a master
control station,
5 monitoring
stations, three ground
antennas & a
Pre launch check
out station
Space
Segment
Space
Segment
consists of 24
satellites
User
Segment
User
Segment
consists of various
GPS receivers
NAVSTAR Global Positioning System
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Control segmentControl segment
5 monitoring stations which passively track & collect
ranging data from all satellites in view.
A master control station which processes the satellite
ranging data to determine satellite orbits and update
the navigation message for each satellite.
3 ground antennas which transmit the updated
navigation message to each satellite .
A pre launch station which supports the satellite pre-
launch compatibility tests and serves as a fourth
ground antenna when necessary.

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29th August 2009
Control SegmentControl Segment
The GPS system used is American NAVSTAR ( NAVigation System by
Timing And Ranging) system
1 master control station, 5 monitoring stations, 1 pre launch station,3 ground
antenna
AFB- AIRFORCE BASE
Note :-all the stations are under the control of U S. Territory &
They are all positioned near the equator
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Space segmentSpace segment
• The space segment consists of 24
operational satellites plus 3 spares

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The Space Segment
Satellite 12 hr. period ..Satellite 12 hr. period ..
24+3
Satellites
24+3
Satellites
Space segment
4 satellite
In each
Orbit
4 satellite
In each
Orbit
Six
Orbits
Six
Orbits
20,200 KM
From
earth
20,200 KM
From
earth
Orbit
inclination
= 55 deg.
Orbit
inclination
= 55 deg.
NAVSTAR System of GPSNAVSTAR System of GPS
hrs
Satellite
makes two
rounds in 24
hrs
*
*
GPS ConstellationGPS Constellation
54

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GPS OrbitsGPS Orbits
12 Hour Period
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Satellite Vehicle No. 27Satellite Vehicle No. 27
Sensors
Sensors
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*

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-45 deg.lat
+ 45 deg. lat
0 deg. lat
+ 70 deg. lat
- 70 deg. lat
NO SV COVERAGE IN THIS
REGION
NO SV COVERAGE IN THIS
REGION
A satellite vehicle is not
stable in the cone of +/ -
70 deg
Its not possible to apply
correction in this cone.
GPS GIVES ERRORS FOR LAT
> +/- 70 DEG.
GPS GIVES ERRORS FOR LAT
> +/- 70 DEG.
29th August 2009
GPS constellation in operationGPS constellation in operation
COMPLETE COVERAGE WITH A MINIMUM OF 5 SV IN VIEW ALL AROUND THE WORLD
EXCEPT NO COVERAGE AT LAT >+ - 70 Deg.
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User SegmentUser Segment
USER SEGMENTUSER SEGMENT
The user segment consists of receivers
and associated support equipment
Receiver processes signals transmitted by
the satellites and Finds:
1. Its Distance from Satellite
2. And calculates Lat, Long, Altitude

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Hand held GPS ReceiverHand held GPS Receiver
General Information related to GPSGeneral Information related to GPS

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CARRIER FREQUENCYCARRIER FREQUENCY
GPS Carrier frequency L1& L2 : 1575.42 MHz and
1277.60 MHz .
These Frequencies are necessary to travel through
ionosphere and troposphere.
SPS – Std. Positioning Service PPS - Precise Positioning Service
SPS has access to codeless L1 signal. (We are SPS users)
PPS user has access to all signals on L1 & L2 and to the
full accuracy of GPS ( only US)
PPS users must have the classified algorithms and the
classified key to remove errors
VELOCITY MEASUREMENTVELOCITY MEASUREMENT
• Velocity is measured using Doppler effect
through software.
• The received frequency appears increased
as the satellite comes towards the
receiver
• Decreases as it recedes from the user.

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EPHEMERISEPHEMERIS
• In a receiver complete check of ephemeris and
storage normally takes 12.5 min to 25 min Max
• The predictions of current satellite positions
transmitted to the user in the data message.
(Orbital data of a satellite vehicle.)
•Ephemeris last for one week
ALMANACALMANAC
• A data file that contains orbit information on all
satellites, clock corrections, and atmospheric
delay parameters.
• It is transmitted by each GPS satellite in order to
facilitate rapid satellite vehicle data acquisition by
GPS receivers.

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GPS -NOTEGPS -NOTE
• Velocity of satellite is approximately 30 km /sec.
• Clock frequency is 100mhz.
• Lat/long calculation is done at the speed of 1 hz.
How GPS Works?How GPS Works?

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Position in Space/ on EarthPosition in Space/ on Earth
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Position in Space/ on EarthPosition in Space/ on Earth

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Aircraft Position determinationAircraft Position determination
Aircraft position in space is found by computing
a/cs distance from 4 satellites
Also all those 4 satellites position from the earth
centre is known.
By knowing above two parameters a/cs position
from earth centre is computed.
From the earth model WGS- 84, comparing the
above results , latitude. Longitude and altitude
can be found.
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29th August 2009
TriangulationTriangulation
TRIANGULATE - MEASURING AND MAP OUT BY DIVIDING IT INTO TRIANGLES
Radius of Earth = 6 378.1 kilometersRadius of Earth = 6 378.1 kilometers

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Result of TriangulationResult of Triangulation
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Earth
Result of TriangulationResult of Triangulation
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Earth

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LATITUDE / LONGITUDE & ALTITUDELATITUDE / LONGITUDE & ALTITUDE
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Triangulation
Summary
Triangulation
Summary
GPS
7676

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29th August 2009 7777ShanksShanks
29th August 2009 7878ShanksShanks

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29th August 2009 7979
29th August 2009 80Shanks

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TWO MEASUREMENTS PUT US
SOMEWHERE IN THIS CIRCLE
TWO MEASUREMENTS PUT US
SOMEWHERE IN THIS CIRCLE
ONE OF THESE TWO
POINTS IS THE
ACCURATE LOCATION
A THIRD SATELLITE
PUTS US AT EITHER OF
TWO POINTS
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SummarySummary
• Thus with the information from four satellites, the Position of the GPS
receiver user is fixed in space or on earth with respect to satellites.
• Triangulation of the above results gives the position with respect to the
centre of earth.
• The altitude of the GPS receiver user is obtained by Subtracting the
radius of earth from the earth centre distance.
• The triangulation result when superimposed on the WGS – 84
software model, gives the latitude & Longitude of the GPS user.
• Thus the GPS user will know his position accurately with respect to
earth. In terms of latitude, Longitude & Altitude.

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January 23, 2017
Thank YouThank You
Shankar11122@gmail.com
9405183808
www.shankarnarayan.co.in

Aircraft Navigation- INS / GPS

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