INS And GPS Flashcards
Is INS a self contained system?
Yes
Can INS be restarted once in Flight?
No
How many systems are in INS for redundancy protection?
3
What is the basic principle of INS?
If you know where an a/c starts from and how far it has moved in any given
Direction then you will also know it’s current position
What movement is along the X-Axis?
Forward
What movement is along the Y axis?
Sideways
What movement is along the Z axis?
Vertically
How is the amount of movement obtained by INS?
A) Acceleration in each direction(acceleration=change in velocity)
B)Duration of application
During interrogation what input does the computer continuously receive?
Input form the aircraft’s magnetic compass system
How does the INS interrogation interpret movement?
Relation to change of latitude and longitude
What information does INS store?
1) Beacon Position
2) Airspace Boundaries
3) Airfield Locations
4) Reporting Positions
What are
1) Beacon Position
2) Airspace Boundaries
3) Airfield Locations
4) Reporting Positions?
Waypoints
What are the flight deck display options available, list all 8
1) A/C track n Groundspeed (TR/GS)
2) Heading n Drift angle (HDG/DA)
3) Distance of Track and track angle error (XTR/TRE)
4) Current Position
5) Distance n Time to next way point(DIS/TIME)
6) !Current wind velocity (WIND)
7) Desired Track next to way point system status (DSRTR/STS)
8) Waypoint intersection and viewing (WAY/PT)
What does the internal Platform contain?
A gyroscope that ensures it remains level with regards to surface of the earth.
What do modern inertial platforms incorporate?
Laser ring gyroscopes
Why have laser ring gyroscopes been incorporated?
To eliminate the problem of drift.
What does the pilot do to his INS prior to taxiing?
Switches on the INS and input s the lat and long, selects align
During alignment the platform levels itself out, True or False?
True.
On completion of alignment the system is selected to nav, True or False?
True.
Any movement of the aircraft prior to electing nav will invalidate the alignment. True or False?
True
What is INS in general?
A stand alone system that uses accelerometers on a gyroscopic platform to calculate movement in all 3 dimensions.
What does GPS stand for?
Global Positioning System
What is GPS?
A Satellite based navigation system made up of a network of up to 32 satellites (places in space by US)
What is GLONASS
24 Satellite System in place by Russia
How often do GPS satellites circle the earth?
Every 12 hours
GOS Satellites transmit information to earth. GPS receivers take Information and use triangulation to calculate the users exact location.
True or False?
True.
What does a GPS receiver do?
Compares time a signal was transmitted with time it was received. Difference tells receiver how far away the satellite is.
GPS is capable of precision approach guidance down to CAT 1.
True or False?
True.
The more satellites in view the more accurate the position. True or False?
True
List the 6 Errors GPS is victim to?
1) Ionosphere + Troposphere delays
2) Orbital Errors
3) Receiver Clock Errors
4) Number of Satellites Visible
5) Satellite Geometry/Shading
6) Single Multi-Path
What are ionosphere n Troposphere delays?
Satellite signals slow as they pass through the atmosphere. (Satellites use a built in average amount of delay)
What are orbital errors?(ephemeris errors)
Inaccuracies of satellite reported position
What is receiver clock errors?
Built in clock can have very slight timing errors
What is number of satellites visible error?
Operates line of sight, of out of sight will cause errors/no position report
What is Satellite geometry/shading?
Ideal satellite geometry exists when satellites are located at wide angles.
Poor geometry exists when satellites are located in a line/tightly grouped
What is single-multi path error?
Occurs when GPS signal is reflected off objects such as tall buildings before reaching receiver. Increase travel time if receiver.
What are the 3 methods for correcting errors?
1) Airborne based augmentation System (ABAS)
2) Ground based augmentation System (GBAS)
3) Satellite based augmentation System (SBAS)
What does ABAS do?
Augments and/or interrogates the information obtained from GNSS elements with other information available on the aircraft
List the two types of ABAS techniques
1) Receiver Autonomous Integrity Monitoring (RAIM)
2) Airborne autonomous integrity monitoring (AAIM)
RAIM GNSS receiver/processor determines the integrity of the GNSS signals without reference to sensors/integrity System other than the receiver itself. Achieved by a check among redundant pseudo range measurement
True
AAIM is where GNSS Information is complemented with on-board sensors and other components
True
What is ground based augmentation System (GBAS)
It is the European system of Local area augmentation System (LAAS)
What is DGPS
Differential GPS
What does DGPS do?
Combines a GPS receiver with a DGPS receiver to create a reference station.
Reference station is a known location and can be determined without any errors.
What is differential correction?
The difference between the measured and calculated ranges of each satellites from the reference station.
The differential corrections for each tracked satellite are formulated/formatted and transmitted to DGPS receivers. The corrections are then applied to the GPS receivers calculations, removing many of the common errors and improving accuracy.
True
What is Satellite based augmentation System (SBAS)?
A term for GNSS augmentation me 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 with ground stations
What is the European SBAS?
EGNOS
What is GPS jamming?
Military will occasionally practise jamming and a NOTAM will be published
When will Galileo be operational?
Circa 2020
What is Galileo?
A global navigation satellite system (GNSS)
Currently being built by the EU and European Space Agency.
Cost €3.4 billion
