Question 223-1 : In civil aviation the height value computed by the receiver of the satellite navigation system navstargps is the ? [ Certification weather ]

Question 223-2 : In relation to the satellite navigation system navstargps the term inclination denotes the angle between the ?

Orbital plane and the equatorial plane.

2606the orbital planes of the satellite navigation system navstargps are inclined 55° to the equatorial plane

Question 223-3 : How long does it take a navstargps satellite to orbit the earth ?

Approximately 12 hours.

2607the 24 satellites that make up the gps space segment are orbiting the earth about 12000 miles above us they are constantly moving making two complete orbits in less than 24 hours these satellites are travelling at speeds of roughly 7000 miles an hourthe orbital period is exactly one half a sidereal day 11 hours and 58 minutes so that the satellites pass over the same locations or almost the same locations every day

Question 223-4 : At what approximate height above the wgs 84 ellipsoid are navstargps satellites circling the earth ?

20200 km.

The satellites are in a nearly circular orbit of the earth at an altitude of 20 200 km 10 900 nm the gps satellites are orbiting the earth in orbits inclined 55° to the plane of the equatorit consists of a notional constellation of 24 operational satellites the satellites are distributed in 6 orbital planes with at least 4 satellites in each the orbital period is exactly one half a sidereal day 11 hours and 58 minutes so that the satellites pass over the same locations or almost the same locations every day

Question 223-5 : In which frequency bands are the l1 and l2 frequencies used by the satellite navigation system navstargps for transmission of the navigation message ?

Uhf.

The navigation message contains almanac data ephemeris satellite clock correction parameters utc parameters ionospheric model satellite health dataeach gps satellite transmits data on two uhf frequencies l1 157542 mhz and l2 12276 mhz l1 is a standard accuracy signal designed for civil users world wide and l2 is a high accuracy signal modulated by a special code for authorised user only

Question 223-6 : In relation to the satellite navigation system navstargps which of the following statements correctly describes the term pseudo random noise prn signal ?

Prn is a code used for the identification of the satellites and the measurement of the time taken by the signal to reach the receiver.

The ca code is a pseudo random noise prn code sequence repeating every millisecond each ca code is unique and provides the mechanism to identify each satellitefor information gps receiver is able to determine the distance to a satellite by determining the difference between the time of transmission by satellite and the time of reception the initial distance calculated to the satellites is called pseudo range because the difference between the gps receiver and the satellite time references initially creates an erroneous range

Question 223-7 : Which of the following navstargps satellite navigation system codes can be processed by unauthorised civil aviation receivers ?

Ca.

This question also appears at the exam under the following statement unauthorised civilian users of navstar gps can access the ca code gps system satellites transmit their signals on two carrier wave l1 and l2l1 is a standard accuracy signal designed for civil users world wide and l2 is a high accuracy signal modulated by a special code for authorised user onlyca code coarse acquisition clear access or civil access is modulated on the l1 carrier only the p code precise or protected is modulated on both carriersl1 157542 mhzl2 12276 mhzl1 is the higher frequency l1 is modulated with the p and ca code

Question 223-8 : Almanac data stored in the receiver of the satellite navigation system navstargps is used for the ?

Fast identification of received signals coming from visible satellites.

The gps almanac is a set of data that every gps satellite transmits and it includes information about the state health of the entire gps satellite constellation and coarse data on every satellite's orbitwhen a gps receiver has current almanac data in memory it can acquire satellite signals and determine initial position more quickly

Question 223-9 : How does a navstargps satellite navigation system receiver recognise which of the received signals belongs to which satellite ?

Each satellite transmits its signal on common frequencies with an individual pseudo random noise code.

Question 223-10 : Which of the following data in addition to the pseudo random noise prn code forms part of the so called 'navigation message' transmitted by navstargps satellites ?

Almanac data satellite status information.

The 'navigation message' provides all the necessary information to allow the user to perform the positioning service ephemeris parameters needed to compute the satellite coordinates with enough accuracy the time parameters and clock corrections to compute satellite clock offsets and time conversions the service parameters with satellite health information used to identify the navigation data set

Question 223-11 : What is the time taken to receive the complete navigation message complete set of data from all satellites ?

125 minutes = 30 seconds per data frame .

Question 223-12 : Which of the following statements concerning the l1 and l2 navstargps transmission frequencies and codes is correct ?

The higher frequency is used to transmit both the ca and p codes.

Gps system satellites transmit their signals on two carrier wave l1 and l2l1 is a standard accuracy signal designed for civil users world wide and l2 is a high accuracy signal modulated by a special code for authorised user onlyca code coarse acquisition clear access or civil access is modulated on the l1 carrier only the p code precise or protected is modulated on both carriersl1 157542 mhzl2 12276 mhzl1 is the higher frequency l1 is modulated with the p and ca code

Question 223-13 : Which one of the following errors can be compensated for by a navstargps receiver comparing l1 and l2 frequencies ?

Ionospheric delay.

This question also appears at exams with the following wording gps receivers using both gps frequencies l1 and l2 can nearly eliminate ionospheric propagation delay ionospheric delay can be compensated by a navstargps 2608influenced propagation of radio waves through the earth's atmospherewhile radio signals travel with the velocity of light in the outer space their propagation in the ionosphere and troposphere is slowerin the ionosphere in a height of 80 400 km a large number of electrons and positive charged ions are formed by the ionizing force of the sun the electrons and ions are concentrated in four conductive layers in the ionosphere d e f1 and f2 layers these layers refract the electromagnetic waves from the satellites resulting in an elongated runtime of the signalsthese errors are mostly corrected by the receiver by calculations the typical variations of the velocity while passing the ionosphere for low and high frequencies are well known for standard conditions theses variations are taken into account for all calculations of positions

Question 223-14 : Concerning the navstargps 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.

Raim is a technique whereby a receiver processor determines the integrity of the navigation signalsraim is achieved by consistency check among pseudo range measurementsbasic raim requires 5 satellites a 6th is for isolating a faulty satellite from the navigation solutionfor information when a gps receiver uses barometric altitude as an augmentation to raim the number of satellites needed for the receiver to perform the raim function may be reduced by one

Question 223-15 : What is the inclination to the equatorial plane of the satellite's orbit in the navstar gps constellation ?

55°.

2606the orbital planes of the satellite navigation system navstargps are inclined 55° to the equatorial plane

Question 223-16 : In respect of the use of gnss dilution of precision dop is a loss of accuracy due to ?

Relative position of the visible satellites.

The position dilution of precision pdop is the geometric effect resulting from satellites being too close together satellites that appear farther apart in the sky provide a more accurate position solution than ones close together in the latter case the position accuracy is degraded in a similar fashion to when position lines from ground based navaids navigational aids are less than 45° since the ephemeris of each satellite is known by the gps global positioning system receiver it is possible to calculate which combination of gps satellites provides the best geometry at a given time this is translated into a figure called the position dilution of precision pdop since the satellites move across the sky relative to the user the pdop is always changing a low pdop is better a pdop of 4 to 6 is considered good position solutions calculated when the pdop is from 6 to 10 should be used cautiously because they may have significant error a pdop that is above 10 indicates unacceptable error com encom062 646jpgthe icao international civil aviation organization states that a pdop of less than 6 is required for en route navigation with a pdop of 3 or less required for nonprecision approaches ie not ils types

Question 223-17 : Which one of the following is an advantages of a multi sensor system using inputs from a global navigation satellite system gnss and an inertial reference system irs ?

The gnss can be used to update the fms position from a drifting irs.

What is a multi sensor system in aviation it's a fmc flight management computer informations received from a gnss are well more accurate than an ins while computing our position from different sources the fmc can use gnss position to continuously correct the information received from the ins we will not correct physically the drift

Question 223-18 : What type of clock is used in navstar gps satellites ?

Atomic.

Question 223-19 : How many clocks are installed in each navstar gps satellite ?

4.

Question 223-20 : What is egnos european global navigation overlay system ?

Wide area differential gps wadgps .

egnos european geostationary navigation overlay service consists of 3 geostationary inmarsat satellites which broadcast gps look alike signalsegnos is designed to improve accuracy to 1 2m horizontally and 3 5 m verticallyintegrity and safety are improved by alerting users within 6 seconds if a gps malfunction occurs up to 3 hrs gps alone wadgps is an acronym for wide area differential gps it's a general term for solutions used to enhance gps accuracy over large areas eg north america or europe wadgps solutions usually use a network of ground based stations that compare their precisely known location with locations calculated from gps satellite signals any differences found can be used to create correction data that's broadcast from satellitessatellite based augmentation systems include egnos in western europe and the mediterranean waas in usa msas in japan gagan in india

Question 223-21 : In accordance with icao annex 10 the navstargps global average 95% position accuracy in sps should be ?

13 m horizontally.

The us department of defense has released the new gps performance standard in october 2001 taking into account the new levels of performance achievable without sa selective availability according to the revised performance standard for gps sps standard positioning service positioning accuracy standards are given as dod 2001 global average positioning domain accuracy = or < 13 meters 95% all in view horizontal error signal in space only = or < 22 meters 95% all in view vertical error signal in space only

Question 223-22 : In relation to the satellite navigation system navstargps all in view is a term used when a receiver ?

Is tracking more than the required 4 satellites and can instantly replace any lost signal with another already being monitored.

Question 223-23 : The gps control segment consists of ?

A master control station monitor stations and ground antennas.

The control segment permits to ensure that the transmitted data of the satellites is controlled and updated from time to time by ground stations main tasks of the control segment are managing sps performance navigation data upload monitoring satellitesthe control segment comprises a master control station ground antenna monitoring stationsfor information the space segment consists of a notional constellation of 24 operational satellites the user segment is the gps receiver side

Question 223-24 : One of the tasks of the gps control segment is ?

To detect the malfunctioning of satellites.

Question 223-25 : 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.

The control segment comprises a master control station ground antenna monitoring stationsthe master control station is responsible for all aspects of the constellation command and controlthe main tasks of the control segment are managing sps performance navigation data upload monitoring satellites

Question 223-26 : 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.

Mask angle is that angle above the horizon below which satellites will not provide a usable signal to the receiverthe mask angle is generally set to 5 degrees as a default although the user is provided with the capability to select other mask angles

Question 223-27 : 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.

The control segment consists of five monitor stations hawaii kwajalein ascension island diego garcia colorado springs three ground antennas ascension island diego garcia kwajalein and a master control station mcs located at schriever afb in colorado the monitor stations passively track all satellites in view accumulating ranging data this information is processed at the mcs to determine satellite orbits and to update each satellite's navigation message updated information is transmitted to each satellite via the ground antennasthese updates synchronize the atomic clocks on board the satellites to within a few nanoseconds of each other and adjust the ephemeris of each satellite's internal orbital model the updates are created by a kalman filter that uses inputs from the ground monitoring stations space weather information and various other inputs

Question 223-28 : The term sbas signifies ?

Satellite based augmentation systems.

the principle of a sbas to measure on the ground the signal errors transmitted by gnss satellites and transmit differential corrections and integrity messages for navigation satellites 2609

Question 223-29 : The term 'gbas' signifies ?

Ground based augmentation systems.

The gbas ground segment consists of three or four gbas reference receivers that are sited typically on or near an airport property these reference receivers track the signals from navigation satellites and pass pseudorange measurements and other information relevant to signal health and system performance monitoring to a central processing facilitythe central processing facility uses the multiple redundant observations of the pseudoranges to compute estimates of the pseudorange corrections for each satellite signal observed by the reference receiversthe central processing facility also monitors the signal integrity and computes parameters for each satellite that the user may use to determine the availability of the signal in space for a desired level of service and a given satellite geometry 2609the differential corrections and integrity information are broadcast to the user

Question 223-30 : The term abas signifies ?

Airborne based augmentation systems.

From the easa detailed theoretical knowledge syllabus and learning objectives abas means airborne based augmentation systems

Question 223-31 : The system capable to measure on ground the signal errors transmitted by gnss satellites and relay the measured errors to the user for correction is ?

Gbas.

The gbas ground segment consists of three or four gbas reference receivers that are sited typically on or near an airport property these reference receivers track the signals from navigation satellites and pass pseudorange measurements and other information relevant to signal health and system performance monitoring to a central processing facilitythe central processing facility uses the multiple redundant observations of the pseudoranges to compute estimates of the pseudorange corrections for each satellite signal observed by the reference receiversthe central processing facility also monitors the signal integrity and computes parameters for each satellite that the user may use to determine the availability of the signal in space for a desired level of service and a given satellite geometry 2609the differential corrections and integrity information are broadcast to the user

Question 223-32 : A sbas satellite based augmentation systems consists of ?

3 elements.

3 elements ground infrastructure sbas satellites and sbas airborne receivers

Question 223-33 : Frequency band of the sbas data link is ?

A signal with the same frequency as gps.

Sbas = same frequencythe frequency band of the data link is identical to that of the gps signals l1 frequency 157542 mhz take care another question asks for the gbas data link frequency band the answer is vhf band of ils and vor systems

Question 223-34 : Sbas systems improve the performance position accuracy of gnssgps receivers by ?

Providing an additional signals coming from the geostationary satellites.

Geostationary sbas satellite based augmentation systems satellites broadcast corrections to the standard data broadcast by gps geo orbital satellites in order to improve the accuracy of the solution obtained from the raw gps data the gps solution obtained from the broadcast gps data using a single frequency receiver will typically have an accuracy within about 3 to 5 meters most of the time using sbas corrections this accuracy can be improved to around the 1 meter mark in typical operationcorrections are calculated using a network of accurately surveyed ground based monitoring systems uploaded to the sbas satellites via ground uplink stations and then broadcast by the sbas satellites on the standard 157542mhz gps l1 frequencycurrent sbas system implementations providing freely available broadcast data are the us wide area augmentation system waas the european geostationary navigation overlay service egnos and the japanese multi functional satellite based augmentation service msbas messages are transmitted from satellites as subframe messages in the same way as navigational data is received from standard gps satellites

Question 223-35 : Egnos european geostationary navigation overlay service is a ?

Satellite based augmentation systems sbas .

Satellite based augmentation systems sbas is sometimes called wide area differential gps wadgps

Question 223-36 : Sbas messages are broadcast via ?

Geostationary satellites.

Question 223-37 : The system capable to measure on the ground the signal errors transmitted by gnss satellites and transmit differential corrections and integrity messages for navigation satellites is ?

Sbas.

the principle of a sbas to measure on the ground the signal errors transmitted by gnss satellites and transmit differential corrections and integrity messages for navigation satellites the principle of a gbas to mesure on ground the signal errors transmitted by gnss satellites and relay the mesured errors to the user for correction

Question 223-38 : A ground based augmentation system gbas supports all phases of approach landing departure and surface operations within an area of coverage of about ?

30 km.

Question 223-39 : Frequency band of the gbas data link is ?

Question 223-40 : 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.

Gbas ground sub systems are intended to provide a precision approach service and optionally they may also provide a gbas positioning servicethe precision approach service is intended to provide deviation guidance for final approach segments while the gbas positioning service provides horizontal position information to support two dimensional 2d rnav operations in terminal areasa ground station at the airport broadcasts locally relevant corrections integrity parameters and approach data to aircraft in the terminal area in the 108 117975 mhz band