NAV - INS & GPS Flashcards

1
Q

What is INS? (4)

A

INS - Inertial Navigation System

  • Uses Rotation sensors to continuously calculate by dead reckoning
  • Dead reckoning the orientation, velocity, of a moving object without the need for external references
  • Cannot be restarted once in-flight so triple systems for redundancy protection
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2
Q

What Axis’s are used for an INS? (3)

A
  • Forwards = X
  • Sideways = Y
  • Vertically = Z

(acceleration = change of velocity)

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3
Q

How does an INS interpret movement? (3)

A
  • Interprets Movement in relation to change of latitude and longitude
  • Receives continuous input from the aircraft’s magnetic compass system

Also:

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4
Q

What can a triangle of velocity show?

A

show that INS instantaneously solves the navigation problem and presents the pilot with instant readings

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5
Q

What can the Pilot input and receive on the flight deck with INS? (8)

A
  • Aircraft track and groundspeed (TR/GS)
  • Heading and drift angle (HDG/DA)
  • Dist. off track and track angle error (XTR/TRE)
  • Current position (POS)
  • Waypoint insertion and viewing (WAY/PT)
  • Distance and time to next waypoint (DIS/TIME)
  • Current wind velocity (WIND)
  • Desired track to next waypoint and system status (DSRTR/STS)
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6
Q

Inertial Platform diagram

A
  • The Mounting Board for the Accelerometers
  • It contains gyroscopes that ensure it remains level with regard to the surface of the Earth
  • Modern systems incorporate laser ring gyroscopes to eliminate the problem of drift
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7
Q

What type of North does the INS find during its alignment? (1)

A

True north

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8
Q

What does the system select when its alignment is completed? (1)

A

“Nav”

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9
Q

What will happen is an Aircraft is moving prior to alignment completion? (2)

A
  • Invalidates the alignment prior to selecting Nav
  • Sequence has to be repeated
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10
Q

INS is a stand-alone system using accelerometers on a gyroscopic platform to calculate movement in all 3 dimensions. True or False?

A

True

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11
Q

What is GNSS? (2)

A

GNSS - Global Navigation Satellite System

  • Satellites providing signals from space that transmit positioning and timing data to GNSS receivers
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12
Q

What types of GNSS global coverage is available? (4)

A
  • Galileo - Europe
  • NAVSTAR - USA
  • GLONASS - Russia
  • BeiDou - China
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13
Q

How often do GPS satellites travel around the Earth? (1)

A
  • Every 12 hours in a precise orbit
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14
Q

How does a GPS work? (4)

A
  • Transmitting signal information to Earth
  • Use triangulation to calculate the user’s exact location
  • Compares time from signal transmission to when the signal is received
  • Time difference tells the GPS receiver how far away the satellite is
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15
Q

What Category level is a GPS capable of being for a precision approach? (1)

A

Capable to Cat I limits

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16
Q

GPS operation diagram

A

The more satellites in view, the more accurate
the position

17
Q

How is the performance of GNSS assessed? (4)

A
  1. Accuracy
  2. Availability
  3. Integrity
  4. Continuity
18
Q

What errors do civilian GPS receivers encounter? (2)

A
  • Ionosphere and Troposphere Delays
  • Orbital errors
19
Q

How do satellites work with their Geometry? (2)

A
  • The wider the angle between the satellites, the better the accuracy of the measurement
  • Poor geometry results when the satellites are located in a line or in a tight grouping
20
Q

What types of geometry / shading error can occur for GPS? (3)

A
  • Receiver clock errors
  • Number of satellites visible
  • Signal multi-path
21
Q

How is satellite geometry / shading corrected? (3)

A
  • ABAS - Airborne based Augmentation System. (RAIM)
  • GBAS - Ground Based (Differential GPS)
  • SBAS - Satellite Based (WAAS, EGNOS)
22
Q

What is ABAS? (3)

A

ABAS - Airborne Based Augmentation System

  • Augments and/or integrates the information obtained from the GNSS elements with other information available on board the aircraft INS
  • Improves: Integrity, availability, accuracy
23
Q

What 2 techniques does ABAS use? (2)

A
  • RAIM - Receiver Autonomous Integrity System
  • LAAS - Local Area Augmentation System
24
Q

What is DGPS? (6)

A

DGPS - Differential GPS

  • Works by placing a GPSreceiver (called a reference station) at a known location
  • Can determine the errors in the satellite signals
  • Measures ranges to each satellite
  • The difference between the measured and calculated range becomes a “differential correction”
  • Corrections are then applied to the GPS receiver’s calculations, removing many of the common errors and improving accuracy
25
Q

What is SBAS? (3)

A

SBAS - Satellite Based Augmentation System

  • A generic term for GNSS augmentations, which use geostationary satellites to broadcast information to users over a large geographical area
  • Similar to DGPS but uses two satellites to further correct readings together with ground stations