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)
When talking about the Galileo GNSS we can say that every satellite has two types of atomic clock:
1 - which are identical.
2 - which are not identical.
3 - where one is the master and one is the slave.
4 - which are not synchronised with each other.
Which of the above is/are correct?
2 & 4
What is true concerning UTC parameters within the navigation message of a NAVSTAR GPS satellite?
They are used for the satellite’s clock correction to convert from satellite-time to GPS time.
How long does it take a GLONASS satellite to orbit the earth?
11 hours 15 minutes
For what reason is a mask angle set-up in a GPS-receiver?
To deny the receiver the use of GPS-satellites with an elevation less than the mask angle.
What difference, if any, is there between NAVSTAR GPS and GLONASS?
GLONASS satellites orbit faster around the Earth than GPS satellites.
Which of the following satellite navigation systems has Full Operational Capability (FOC) and is approved for specified flights under IFR conditions in Europe?
NAVSTAR/GPS
What is the function of the control segment in GPS NAVSTAR?
To ensure the transmitted data of the satellites is controlled and updated from time to time by ground stations.
GBAS ground subsystems provide two services, the precision approach service and the GBAS positioning service. The precision approach service provides:
deviation guidance for Final Approach Segments.
The required 30 Galileo operational satellites are located on:
3 orbital planes with 9 satellites and 1 spare replacement in each plane.
At what approximate height above the WGS 84 ellipsoid are Galileo satellites circling the Earth?
23 200 km
The influence of the ionosphere on the accuracy of the satellite navigation system NAVSTAR/GPS is:
minimised by the receiver using a model of the atmosphere and comparing signals transmitted by the satellites
In relation to the satellite navigation system NAVSTAR/GPS, the term ‘inclination’ denotes the angle between the:
orbital plane and the equatorial plane
Which of the following NAVSTAR/GPS satellite navigation system codes can be processed by ‘unauthorised’ civil aviation receivers?
C/A
Which of the following geometric satellite constellations provides the most accurate NAVSTAR/GPS position fix?
3 satellites with a low elevation above the horizon and an azimuth of 120° from each other together with a fourth directly overhead
One of the tasks of the GPS control segment is
to determine and send new ephemeris and new satellite clock error data to the GPS-satellites.
Which of the following statements about the accuracy that can be obtained with the LAAS (local area augmentation system) of the satellite navigation system NAVSTAR/GPS is correct?
The closer the receiver is to a LAAS ground reference station, the more accurate is the aircraft position fix.
The frequency band of the Galileo GNSS is:
1164 - 1215 MHz, 1260 - 1300 MHz, 1559 - 1591 MHz
In a Satellite-Assisted Navigation System (GNSS/GPS), a fix is obtained by:
measuring the time taken for a minimum number of satellites’ transmissions, in known positions, to reach the aircraft’s receiver
Which of the following coordinate systems is used by the NAVSTAR/GPS receiver to calculate position (latitude, longitude and altitude)?
WGS 84
In relation to the NAVSTAR/GPS satellite navigation system, ‘Search the Sky’ is a:
procedure that starts after switching on a receiver if there is no stored satellite data available
Which of the following procedures must be adopted if, on a flight under IFR conditions using a NAVSTAR/GPS satellite navigation system receiver, the position fix obtained from the GPS receiver differs from the position of conventional navigation systems by an unacceptable amount?
It may be continued using conventional navigation systems
In the ‘timing section’ of the Galileo satellite system, how many clocks have been developed?
2 clocks have been developed, a Rubidium Frequency Standard clock and a Passive Hydrogen Maser clock.
Which statement concerning Galileo GNSS is correct?
GPS, EGNOS and GALILEO are compatible, with not interfere with each other, and the performance of the receiver will be enhanced by the interoperability of the systems.
Which of the following statements is correct regarding Galileo satellites?
1 - In each satellite there are two identical atomic clocks.
2 - In each satellite there are two types of non-identical atomic clock.
3 - In each satellite there is one master atomic clock and one reference clock.
4 - The clocks of the satellites are synchronised with each other.
5 - The clocks of the satellites are synchronised with a network of clocks which are located on the ground.
2
The required 24 NAVSTAR/GPS operational satellites are located on:
6 orbital planes with 4 satellites in each plane
An SBAS (Satellite Based Augmentation System) consists of:
3 elements.
The term “GBAS” signifies:
Ground Based Augmentation Systems.
In civil aviation, the height value computed by the receiver of the satellite navigation system NAVSTAR/GPS is the:
height above the WGS-84 ellipsoid
The main task of the user segment (receiver) of the satellite navigation system NAVSTAR/GPS is to calculate receiver position by:
selecting appropriate satellites automatically, to track the signals and to measure the time taken by signals from the satellites to reach the receiver
Which statement about a Satellite Based Augmentation System (SBAS) is correct?
SBAS is able to provide guidance for precision approaches.