GNSS/GPS Flashcards
Name the 3 segments in the GPS system architecture.
Space- satellites
Ground- ground based tracking and system adjustment
User- receiver and processor
State the number of satellites in a fully operational constellation with global coverage.
24
How many times per day does a satellite orbit the earth?
Twice
Who monitors the satellite constellation status and corrects for any errors?
Master Control Station (MCS)
What is Ephemeris?
Information transmitted by satellites about their location (current and predicted), timing and ‘health’.
What is the minimum number of satellites a receiver requires before it can calculate:
a. 2D position?
b. 3D position?
a. 3
b. 4
What is the name given to the type of code used in the GPS signal?
Pseudo random codes. (Though they are actually very well defined and predictable)
Name 7 errors that can degrade the accuracy of the system.
- Ephemeris
- Clock
- Receiver
- Atmospheric/ionosphere
- Multipath
- Masking function
- Selective availability
What is the definition of ‘integrity’ when describing the performance criteria of a navigation satellite?
Ability of the system to provide timely warnings to the user when the equipment is unreliable for navigation purposes.
What does RAIM mean?
Receiver Autonomous Integrity Monitoring
Describe the function RAIM in GPS receiver software?
RAIM provides integrity by detecting the failure of a GNSS satellite.
What is the minimum number of satellites a receiver needs before RAIM can be effective?
RAIM (FD) requires 5 satellites. FDE requires 6.
Does a large PDOP indicate the chance of a high level of accuracy or a low level of accuracy?
Low level of accuracy.
If cruising in CTA, at what period after RAIM loss must ATC be notified?
5 minutes
Can a TSO C-129 receiver be used as a sole and primary means of navigation?
Yes, however provision for alternate planning may not be based on RNAV approach capability.
When conducting a GPS arrival, what conditions must be met?
Primary azimuth guidance must be provided by an associated VOR or NDB.
Is it permissible to make a GPS arrival when the destination azimuth aid is u/s?
No
Masking disregards signals from satellites below the angle of?
TSO 129 specified a mask angle of 7.5 degrees.
If the satellite and receiver clocks and out of synchronisation by 1/1000th of a second, the distance measurement could be in the order of?
More than 150NM
The PDOP for enroute IFR navigation required is?
Less than 6
What are the airworthiness requirements for GPS to be used for enroute IFR?
- TSO C129, C129A, C145A or C146A
- Fitted in accordance with AC21-36 and automatic barometric aiding options functional.
- Instructions carried on board.
