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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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1a. Identify the principles of navigation systems
with at least 80% accuracy
Overview
Purpose
Terms
Navigational Measurements
Inertial Navigation
Radio Navigation
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1a. Identify the principles of navigation systems
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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
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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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1a. Identify the principles of navigation
systems with at least 80% accuracy
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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1a. Identify the principles of navigation
systems with at least 80% accuracy
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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1a. Identify the principles of navigation
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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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1a. Identify the principles of navigation
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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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1a. Identify the principles of navigation
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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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1a. Identify the principles of navigation
systems with at least 80% accuracy
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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1a. Identify the principles of navigation
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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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1a. Identify the principles of navigation
systems with at least 80% accuracy
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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1a. Identify the principles of navigation
systems with at least 80% accuracy
Terms
Steerpoints
Zulu Time Time-Over-Steerpoints
Azimuth steering
Steer-to-indication
Steer-from
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1a. Identify the principles of navigation
systems with at least 80% accuracy
Navigational Measurements
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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1a. Identify the principles of navigation
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Navigational Measurements
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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1a. Identify the principles of navigation
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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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1a. Identify the principles of navigation
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Navigational Measurements
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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1a. Identify the principles of navigation
systems with at least 80% accuracy
Navigational Measurements
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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1a. Identify the principles of navigation
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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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1a. Identify the principles of navigation
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Navigational Measurements
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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1a. Identify the principles of navigation
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90
Navigational Measurements
Relative Bearing
Angular direction measured from one
position to another
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1a. Identify the principles of navigation
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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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1a. Identify the principles of navigation
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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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1a. Identify the principles of navigation
systems with at least 80% accuracy
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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1a. Identify the principles of navigation
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Inertial Navigation Mechanical Gyro
Balance maintained
by spinning mass Resist lateral
movement.
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1a. Identify the principles of navigation
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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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1a. Identify the principles of navigation
systems with at least 80% accuracy
Inertial Navigation Standard INS
Mechanically establishes
a stable platform thatremains oriented with theearths gravitational field(horizontal axis)
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1a. Identify the principles of navigation
systems with at least 80% accuracy
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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1a. Identify the principles of navigation
systems with at least 80% accuracy
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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1a. Identify the principles of navigation
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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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1a. Identify the principles of navigation
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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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1a. Identify the principles of navigation
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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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1a. Identify the principles of navigation
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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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1a. Identify the principles of navigation
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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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1a. Identify the principles of navigation
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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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1a. Identify the principles of navigation
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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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1a. Identify the principles of navigation
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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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1a. Identify the principles of navigation
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Summary Purpose of Navigation
Terms
Navigational Measurements
Inertial Navigation
Radio Navigation
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