egi-ins part 1

8/12/2019 Egi-Ins Part 1

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Unit 1. Embedded Global

Positioning System; Inertial

Navigation System

1a. Identify the principles of navigation systems

with at least 80% accuracy.


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with at least 80% accuracy

Overview

Purpose

Terms

Navigational Measurements

Inertial Navigation

Radio Navigation


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with at least 80% accuracy

Purpose

Navigation is the art and science of conducting

an aircraft expeditiously and safely to a specificdestination


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1a. Identify the principles of navigation

systems with at least 80% accuracy

Terms

Coordinate system

(position) Latitude

0

30

60

+90

-90

60

30

Run East to West

Reference for LatitudeIs the equator (0 deg)

MeasureNorth

ToSouth


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Terms

Coordinate system (position)

Longitude

Reference

is thePrime

Meridian0 degrees

International Date Line+ 180 degrees

Run north to south

Greenwich,England

MeasureEast

toWest

90120150180 3060 0


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Terms

Latitude stated first in

degrees / minutes Followed by Longitude

N 33 58.9

W 98 20.4

0

30

60

+90

-90

60

30

90120150180 3060 0


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Terms

Measuring in degrees

Degrees

Symbol:____

360 in a complete circle

Minutes

Symbol:___

60 in one degree 1 cannot exceed 60

61 = 1 1

Tenths of minutes

32 28.1


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Terms

Nautical Mile

One Nautical Mile (nm) equals: 1 minute of longitude (only at the equator)

6076.1 ft

It is the primary navigation measurement for distance


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Terms

Nautical Mile

Latitude and the nautical mile (nm) Measurement is constant all the way to the poles

One minute of latitude, anywhere, equals one nautical mile

Longitude and the nautical mile (nm)

Measurement is NOT constant

One minute of longitude decreases in distance when approaching thepoles (converge)

One minute of longitude is only equal to 1nm when measured at the

equator


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Example calculating destinations

Plot destination if next destination was 10 Nm north of the aircraft

NS

W

E

STPT 1

Selected destination pointCurrent position

Latitude1Nm = 1 minute (always)

Add 10 Nm to current Latitude

Start


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Terms

Great Circle Steering

Aircraft navigationcomputes destinationsusing great circle steering

computations

Greatest circle on any sphere isa great circle

Great circles divide theearth in two equal halves

Greatest circle are theshortest distance navigatingpoint to point on a sphere


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Terms

Altitude

Measures aircraft elevation Above sea level (Mean Sea Level:MSL)

Above ground level (AGL)

Modes of operation dictate which altitude is used or calculated

Always measured in feet


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Terms

Steerpoints

Zulu Time Time-Over-Steerpoints

Azimuth steering

Steer-to-indication

Steer-from


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Reference planes

Horizontal Planes: X Y-Used to determinemovement in N, S, E and W

direction

Vertical Plane: Z-Used to determine movement ininertial altitude

X

Y

Z

NE

W SStart


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Speed- rate of motion

Velocity (ft/sec or Nm/hr)

Includes both speed and direction

Horizontal (X and Y axis)

Vertical (Z axis)

Acceleration (ft/sec2) change in velocity

Ground speed Slant Range

Gravity

Force which pulls bodies towards the center of the earth

G force represents force of gravity exerted on all objects

The higher the g number the more force is exerted


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Navigational Measurements Attitude The orientation of an aircrafts axis relative to a reference line

Horizon line- Reference that is parallel toearths surface against which pitch and rollis displayed

Normal Axis

Aircraft Axis


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Normal Axis

Pitch

Pitch-Imaginary pivot along lateral

axis (wing to wing)-Measures Nose up (+90)and nose down (-90)

Azimuth-Vertical Z axes (yaw) passesthrough the center of gravity

Roll-Imaginary pivot alonglongitudinal axis (nose to

tail). Measures to + 180 deg

Left Wing Down, counterclockwise, negative roll (-)

Right Wing Down,clockwise, positive roll (+)

Roll AzimuthClick to activate


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HeadingWhere the nose of the aircraft is

pointing along the horizontalreference planes (X & Y); North,South, East or West

Compass360deg

Cardinal PointsN = 0degE = 90degS= 180deg

W = 270deg

Magnetic Northstandard for allNavigationheadings(compass)

(Reference is North Pole) N(0)

E(90)

S(180)

W(270)

True North(Earths spin axis)standard forLat/Long (maps)


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Navigational MeasurementsMagnetic North

Magnetic VariationAngular difference betweenmagnetic north and true north

N(0)

E(90)

S(180)

W(270)

True North

Converts true heading to magheading for use with conventionalaviation

Based on present position (incr

the further north you fly)

Mag/Var is automaticallycomputed within the F-16navigational computer

Its necessary for pilots using

magnetic instruments withstandard maps (true north)


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NE

CourseThe ground track which an aircraft is

flying (not heading)Reference is the North poleDrift due to winds (sideslip)

E

SE

Heading

adjusts tomaintain a

course

N(0)

E(90)

S(180)

W(270)


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90


Relative Bearing

Angular direction measured from one

position to another


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Inertial Navigation A primary navigation system computes the following:

Velocity (groundspeed not airspeed)

Acceleration Attitude

Position

Inertial Altitude

Distance to destination


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It is a self contained operating systemusing a stable platform assy

Operates independent of theenvironment

System designed to measure movementbased on:

Principles of inertia

Newtons laws of motion

Objects tends to maintain a state ofmotion (at rest or in a straight line)unless a force is applied

Acceleration is dependent on an objectsmass and the force applied to it

For every action there is an equal andopposite reaction


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Inertial Navigation

Basic Components

Accelerometers

Primary measuring device

Pendulous device:

Z

Y

X

Pendulum, due to inertia, tends to swing away from itsneutral position when movement occurs

10

0

5 15

Signal Pickoff Device Tells how far the pendulum device has movedThe greater the distance, the greater the acceleration

Force

0

5 15

10

Acceleration

0

5 15

10

Please Wait


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Inertial Navigation Mechanical Gyro

Balance maintained

by spinning mass Resist lateral

movement.


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Ring Laser Gyro (RLG) Use lasers traveling in opposite directions within the same ring

Laser traveling in same direction of rotation has a longer distance to travel

Laser traveling in opposite direction has a shorter path to travel; the beam and thedetector are converging towards each other (shorter distance)

Variance in the lasers frequencies is proportional to the amount of rotation

Rotate Lasers


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Inertial Navigation Standard INS

Mechanically establishes

a stable platform thatremains oriented with theearths gravitational field(horizontal axis)


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Inertial Navigation Gimbals (4 each)

Connected to the airframe

serving as a ball & socket jointbetween thegyros/accelerometers and theaircraft

Allow platform to move 360 degin all directions

Operate conjunctly with thegyros keeping a level platform


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Inertial Navigation Mechanical Gyro

Orient to keep the

platform level to theearth at all times

Allow the stableplatform to operateindependently of theenvironment

The leveled platformrepresents the horizonline

Gyros


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Inertial Navigation Accelerometers

3 mounted on a

stabilized platform Measure aircraft

acceleration alongeach axis

Z

YX

2 Accelerometers (Horizontal axis)

1 Accelerometer (Vertical axis)


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Inertial Navigation Ring Laser Gyros

One per axis

Determines rotation about3 axes

Output of rotation andacceleration used todetermine requiredinformation bymathematical equations

Does not have mechanicallimitations of the StandardINS

Z

Accelerometers

YAW

Roll

PitchY

X


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Inertial Navigation Radial Error Rate (RER)

The amount of drift an inertial navigation unit has incurred over a period

of time (NM/hour) Drift

The angular tilt of the platform inducing velocity errors

This is due to an accumulation of small platform errors over a period oftime

Observable errors:

Heading

Position(Lat/Long)

Velocity (X,Y, and Z)

RER rate is 1.6 NM/hour


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Radio Navigation Local Ground or Airborne system

N32*55.9 W98*20.4NS

W

E

Once Signal is received aircraft is able to determine:

Start


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Radio Navigation Global positioning system (GPS)

Elements include:

Ground Stations: Located around the worldTransmit signals to the satellites

Keep the satellite constellation functioning

Satellite Network: 24 equally spaced satellites

Satellites orbit the earth in 12 hours

Each satellite continually transmits: Its location

Time marker

Orbit data/Almanac data

Airborne GPS Receiver: Installed in the aircraft

Only receives signals from visible satellites


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Radio Navigation Satellite Ranging

The Receiver receives and decode satellite signals

Measure time for signal to travel from satellite to receiver Multiply travel time by signal speed = distance to satellite

Know the distance to four satellites and precise 3D position can becalculated

Calculate speed by measuring movement since last position calculation

GPS will calculate and provide the following: Present position: Latitude & Longitude

Altitude

Velocity

Time


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Radio Navigation GPS Receiver tracking sequence:

Receiver searches for satellites and determines which ones are visible

Visibility is based on: User entered predictions of (PVT)

Present Position

Velocity

Time

Stored Almanac data (via DTC)

Almanac Data (from satellites)

Satellites orbit data and health info

Allows GPS receiver to know where satellites are: Receiver Position

Current date

Current time

Continually updated by satellites


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Radio Navigation GPS Receiver tracking sequence:

If Almanac data is Not available or poor PVT predictions entered:

Receiver must search the sky for satellites (up to 90minutes) Receiver locks onto any satellite in view

Downloads new almanac data

Initializes Tracking Sequence


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Summary Purpose of Navigation

Terms


Inertial Navigation

Radio Navigation

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