06 GNSS Flashcards
ATPL RADIO
Which statement about a Satellite Based Augmentation System (SBAS) is correct?
SBAS is able to provide approach and landing operations with vertical guidance.
How long does it take a Galileo satellite to orbit the earth?
14 hours
What is EGNOS (European Global Navigation Overlay System)?
Wide Area Differential GPS (WADGPS)
…………………………………
The European geostationary navigation overlay system (EGNOS) is a satellite based augmentation system (SBAS), i.e. it is using geostationary satellites to transmit correction signals to global navigation satellite system (GNSS) receivers. As these satellites transmit their signals cover a large area, EGNOS is a wide area differential GPS system.
SBAS messages are broadcast via:
geostationary satellites.
…………………………………..
The satellite based augmentation system (SBAS) use geostationary satellites to transmit error corrections to satellite navigation receivers within their coverage. By using geostationary satellites, their coverage area will be constant and significantly larger than the coverage area of a ground based augmentation system (GBAS).
With reference to GNSS, the ground based augmentation system (GBAS) sends corrections for:
errors due to ionospheric and tropospheric disturbances.
……………………………………
Which of the following statements about the ‘visibility’ of NAVSTAR/GPS satellites is correct?
It varies, depending on the time and observer’s location
…………………………………………………
The visibility of NAVSTAR/GPS satellites is depending on the location of the observer and the time. As the satellites are in constant movement there will be a varying number of satellites in view at any time. Generally, the coverage will be the lowest in the polar regions.
Which statement is correct about the SBAS (Satellite-Based Augmentation Systems)?
In an SBAS the pseudo range corrections are sent to the users by geostationary satellites.
When considering a GPS navigation system the following is true:
For precise position fixing the satellite clock error is very important.
GPS time can be converted to UTC by application of the:
UTC parameters sent in the navigation message.
How many clocks are installed in each NAVSTAR GPS satellite?
4
……………
Present generation NAVSTAR/GPS satellites have 4 rubidium atomic clocks.
Consider SBAS and GBAS:
SBAS can cover more area than GBAS.
The reason why the measured distance between a NAVSTAR/GPS satellite navigation system satellite and a receiver is called a ‘Pseudo-Range’ is because the:
calculated range includes receiver clock error
The term ‘SBAS’ signifies:
Satellite Based Augmentation Systems.
………………………….
There are two types of augmentation systems for satellite navigation:
- Ground based augmentation system (GBAS)
- Satellite based augmentation system (SBAS)
What advantage is there, if any, of using a combination of EGNOS and GPS?
To improve the integrity by alerting users within 6 seconds instead of 3 hours.
Which information about the NAVSTAR GPS is correct?
Note: the orbital heights are approximate values
Satellites: 24, Orbital planes: 6, Orbital height: 20 200 km
………………………….
The NAVSTAR GPS constellation has the following properties: Satellites: 24, Orbital planes: 6, Orbital height: 20 200 km
Which of the following data, in addition to the Pseudo Random Noise (PRN) code, forms part of the so called ‘Navigation Message’ transmitted by NAVSTAR/GPS satellites?
almanac data; satellite status information
……………………………………………
The navigation message from a NAVSTAR/GPS satellite contain almanac data and satellite status information. The receiver clock error is calculated by the receiver based on the signals from several satellites.
GPS system satellites transmit their signals on two carrier waves 1575 MHz and 1227 MHz and supply two possible codes accessible according to user (civil or military). Commercial aviation uses:
only the 1575 MHz carrier wave and one code
…………………………………..
The NAVSTAR/GPS satellites transmit two signals:
L1 – 1575.42 MHz
L2 – 1227.60 MHz
The L1 signal contain the C/A code (coarse acquisition code) for civilian use in addition to the P code (precision code), reserved for military use. The L2 signal has been P code only but there is now a new, civilian L2C code available from newer satellites and the P code is changing to M code.
Which information about the Galileo system is correct?
Note: the orbital heights are approximate values
Satellites: 30, Orbital planes: 3, Orbital height: 23 200 km
Which of the following statements concerning the L1 and L2 NAVSTAR/GPS transmission frequencies and codes is correct?
The higher frequency is used to transmit both the C/A and P codes
Which of the following, if any, is a prerequisite if a receiver of a NAVSTAR/GPS satellite navigation system is to be used in combination with a multi sensor system?
The prescribed IFR-equipment must be installed and operational
In accordance with ICAO Annex 10 the NAVSTAR/GPS global average 95% position accuracy in SPS should be :
13m horizontally
Which of the following is the datum for altitude information when conducting flights under IFR conditions on airways using the NAVSTAR/GPS satellite navigation system?
Barometric altitude
………………………………
Regardless of type of navigation system, barometric altitude (either based on QNH or 1013 hPa) is the reference for altitude in aircraft. The only time GPS altitude can be of limited use is in the event of a total altimeter failure in the aircraft.
Concerning the NAVSTAR/GPS satellite navigation system, what is the meaning of the term ‘Receiver Autonomous Integrity Monitoring’ (RAIM)?
It is a technique by which a receiver ensures the integrity of the navigation information.
What is the time taken to receive the complete Navigation Message (complete set of data) from all satellites?
12.5 minutes (= 30 seconds per data frame)