Question 225-1 : Assume that one of the satellites used by a gps receiver is faulty when the signals of 5 satellites are received including the faulty one the raim software in the receiver ? [ Certification weather ]

Question 225-2 : Aaim aircraft autonomous integrity monitoring is a type of airborne based augmentation system that… ?

Relies on gnss information as well as information from additional on board sensors.

Aircraft autonomous integrity monitoring aaim aaim is a method of monitoring the integrity of the gnss position data using information from on board sensors such as barometric altitude data irs position data and conventional nav aid autotuning vor dme position data this can allow our aircraft to notice any suspicious gnss position data and notify the pilots that it may not be correct it is a type of abas aircraft based augmentation system

Question 225-3 : Which statement from the choice below characterises a satellite based augmentation system sbas ?

Sbas is able to provide approach and landing operations with vertical guidance.

Satellite based augmentation systems sbas sbas uses the idea of differential gps dgps and spreads it over a much wider area than gbas can do their geosynchronous orbits mean that they stay over the same place on the earth all the time and can reduce gnss errors and increase integrity over a very large area this means that there are multiple around the world waas for the usa egnos for europe gagan for india msas for japan etcaccuracy is enhanced through the transmission of wide area corrections for gnss range errors such as ephemeris satellite clock errors and ionospheric propagationsbas systems include reference stations which are geographically distributed throughout the sbas service area receive gnss signals and forward them to the master station since the locations of the reference stations are accurately known the master station can accurately calculate gnss corrections over a wide areasbas can be used to make aircraft gnss systems far more accurate on approaches to allow for lower minimums on instrument approaches using this system they are able to give vertical guidance on approaches also similar to the role of baro vnav on lnavvnav approaches they can even be used to refine the gnss signal for lpv approaches localiser performance with vertical guidance which have decision heights as low as 200ftto tune into a gnss approach with sbas augmentation a 5 digit channel is entered into the guidance system which then accesses the correct information to augment the gnss signal as required this 5 digit code will be given on any relevant approach plate along with the sbas that is to be used such as egnos for europe

Question 225-4 : The fully operational galileo global navigation satellite system gnss will consist of 1 satellites in 2 orbital planes at an altitude of 3 km which are the correct values for 1 2 and 3 ?

1 30 satellites 2 3 orbital planes 3 23222 km.

Refer to figuregalileo is the gnss system set up by europe and a good way to remember it is that there are 3 sets of 3s 30 satellites 3 orbital planes at an orbital altitude of 23222km this number can be quoted slightly different in some publications but is always close

Question 225-5 : Which statement about satellite based augmentation systems sbas is correct ?

The use of sbas improves both the accuracy and the integrity of the position of the user.

Satellite based augmentation systems sbas sbas uses the idea of differential gps dgps and spreads it over a much wider area than gbas can do their geosynchronous orbits mean that they stay over the same place on the earth all the time and can reduce gnss errors and increase integrity over a very large area this means that there are multiple around the world waas for the usa egnos for europe gagan for india msas for japan etcaccuracy is enhanced through detection of errors and the transmission of wide area corrections for gnss range errors such as ephemeris satellite clock errors and ionospheric propagationintegrity is enhanced by the sbas network quickly detecting satellite signal errors and sending alerts to receivers that they should not track the failed satellite an integrity warning is sent after just 6 seconds when using sbas but is up to 3 hours when using standard gnss onlysignal availability can also be improved as the sbas transmits ranging signals from its satellites on top of its other roles it acts as an extra gnss satellitesbas systems include reference stations which are geographically distributed throughout the sbas service area receive gnss signals and forward them to the master station since the locations of the reference stations are accurately known the master station can accurately calculate wide area corrections

Question 225-6 : How is the final approach segment fas of a gbas precision approach procedure defined ?

The gbas ground facility transmits the approach path guidance parameters to the gbas equipped aircraft.

The message transmitted form the gbas ground facility to the aircraft contains one or more data sets that contain final approach segment fas dataeach data set is transmitted with the associated verticallateral alert limits fas ma vertical alert limit fasval fas ma lateral alert limit faslal each final approach segment fas data block contains the parameters that define a single precision approachit is self contained and includes a means to preserve integrity from the time it is generated and validated to the time that it is used in airborne equipmentall of the information necessary to describe the paths and its designation is contained within itthis primarily includes the following airport identification runway designation and position procedure type provides flexibility for advanced procedures such as departure or curved approach procedure name runway surveyed points defining the fas path the fas path is a line in space defined by the following parameters landing threshold point or fictitious threshold point ltpftp flight path alignment point fpap ltpftp height threshold crossing height tch glide path angle gpa

Question 225-7 : The navigation message of a gps satellite contains the parameters of the model of the ionosphere this enables ?

The receiver to calculate the delay of gps signals passing through the ionosphere.

Not only do gnss satellites transmit prn pseudo random noise timing and identification data they also transmit a whole array of navigational data to the receiver called the nav message the nav message is sent in 25 frames of 30 seconds each so takes 125 minutes in total to download to the receiverthe information included in the nav message is almanac non precise data about where the satellites should be at any one time this does not need to be updated very often ephemeris precise data about the exact locations of each satellite held in each satellite separately satellite clock correction correction data for any errors within the satellite clocks utc correction time difference between utc and the gps time ionospheric model a mathematic model of the ionosphere based on an 11 year solar cycle which allows the receiver to calculate out any large errors that occur due to the prn signals slowing down through the ionosphere this is not a perfect system as the ionosphere is not 100% predictable but is far better than no correction satellite health status either healthy usable or unhealthy unusable

Question 225-8 : What is the minimum number of satellites required by a gps in order to obtain a three dimensional fix ?

4.

Satellite navigation is based on a global network of satellites that transmit radio signals in medium earth orbit the basic gps service provides users with approximately 78 meter accuracy 95% of the time anywhere on or near the surface of the earth to accomplish this each satellite emits signals to receivers that determine their location by computing the difference between the time that a signal is sent and the time it is received travelling at 300000 kmsec the receiver uses the time difference between the time of signal reception and the broadcast time to compute the distance or range from the receiver to the satellite with information about the ranges to 3 satellites and the location of the satellite when the signal was sent the receiver can compute its own three dimensional position pay attention the clock on the gps receiver might not be as accurate as the atomic clock on the gps satellite creating a very slight accuracy problem clock error gps satellites broadcast two codes the coarseacquisition ca code which is unique to the satellite and the navigation data messagethe codes contain information the receiver needs to determine latitude longitude and altitude and to synchronise its quartz clock with gps time used through the gps system current approvals for the use of gps equipment in ifr operations require gps derived data to be in the wgs 84 coordinate system or worldwide geodetic datum standard 84summary using range from 3 satellites accurate 2d position fix is obtained lat long time using range from 4 satellites accurate 3d position fix is obtained lat long altitude time

Question 225-9 : Which of the following satellite navigation systems has full operational capability foc and is approved for specified flights under ifr conditions in europe ?

Navstargps.

Learning objective 06206010101 state that there are four main gnsss these are usa navigation system with timing and ranging global positioning system navstar gps russian global navigation satellite system glonass european galileo under construction chinese beidou under construction we have to go with whatever the learning objective says on this and as the most recent lo states that only navstargps and glonass are functional any other options are not correctglonass is not certified for use in europe for many reasons the trust in the system is very low and it does not use the wgs 84 database so is not easily compatible with other gnss systems such as navstargps which is proven and well certified

Question 225-10 : Errors in gps satellite orbits are due to ?

The solar wind and the gravitation of the sun moon and planets.

Learning objective 06206010307 state that errors in the satellite orbits are due to solar winds gravitation of the sun and the moonthese are the effects which can cause changes in the orbits of gnss satellites or any satellite the gravitational ones can be modelled to know when they might occur but solar winds are much more difficult to forecastrealistically as long as a satellite is accurately tracked to update its orbit these effects are usually quite miniscule and none consequentialnote it is unknown whether the current question on easa 2020 syllabus contains the planets as having a gravitational effect as this was removed from the learning objectives in the transition to new syllabus

Question 225-11 : One of the advantages of a satellite based augmentation system sbas over a ground based augmentation system gbas is ?

The coverage area of an sbas is much larger than that of a gbas.

Gbas ground based augmentation systemgbas is a system that attempts to reduce the natural errors within the gnss system by providing very localised augmentation to the satellite signals via a vhf data broadcast vdb that a suitably equipped aircraft can receive and use to fix any position errors it is also called differential gps and can correct for errors induced by satellite clocks ephemeris and ionospheric propogation to make the augmented gnss signal very accuratethese are measurable errors which are measured by multiple receiver antennas and interpretted by a ground station usually located at an airport which can make use of this highly accurate gnss errors in the receiver multipath signals and some small atmospheric propogation errors can still occur but the intention is to get the accuracy below 1m for aircraft on final approach the gbas can also give integrity warnings about faulty satellites as it should be able to detect any such faults at the nearby antennasgbas is limited in the fact that it is very short range spanning approximately 20 nm 30 km according to the old syllabus away from the relevant ground station although there is the capability for a network of such stations in the futuresbas satellite based augmentation systemsbas uses the idea of differential gps dgps and spreads it over a much wider area than gbas can do their geosynchronous orbits mean that they stay over the same place on the earth all the time and can reduce gnss errors and increase integrity over a very large area this means that there are multiple around the world waas for the usa egnos for europe gagan for india msas for japan etcsbas works in a very similar way to gbas but the reference antennas send their corrections to a master control station which communicates the wide area corrections to the geostationary satellites for effective distribution over their large usable areasbas can also give integrity warnings in the same way that gbas can bringing the alerting time down from a potential 3 hours for standard gnss to 6 seconds for sbas users

Question 225-12 : In relation to the navstargps satellite navigation system what is involved in the differential technique d gps ?

Fixed ground stations compute position errors and transmit correction data to a suitable receiver on the aircraft.

Differential gps dgps dgps differential gps is a method of augmenting gnss signals to remove measurable errors such as satellite clock error ephemeris and ionospheric propogation effects this is done by placing multiple reference antennas on the ground in the region that is to be used then measuring their gnss computed position against their actual known position then calculating the corrections to be made to each satellite's pseudo range this allows accuracies of around 1 m in many cases and is the technique used by gbas ground based augmentation systems for small area aviation use cases as well as sbas satellite based augmentation systems for large area dgps uses receiver errors multipath signals and some small atmospheric propogation errors cannot be accounted for but they do not affect the accuracy too much dgps systems like gbas and sbas can also be very useful for monitoring the integrity of gnss satellites as they are constantly monitoring the signals and can give loss of integrity alerts in 6 seconds rather than a potential 3 hours for standard gps

Question 225-13 : When a gps position is augmented by egnos what time to alert can be expected after a loss of integrity ?

6 seconds.

Satellite based augmentation systems sbas sbas uses the idea of differential gps dgps and spreads it over a much wider area than gbas can do their geosynchronous orbits mean that they stay over the same place on the earth all the time and can reduce gnss errors and increase integrity over a very large area this means that there are multiple around the world waas for the usa egnos for europe gagan for india msas for japan etcaccuracy is enhanced through the transmission of wide area corrections for gnss range errors detected by a network of ground antennas such as ephemeris satellite clock errors and ionospheric propagationintegrity is enhanced by the sbas network quickly detecting satellite signal errors and sending alerts to receivers that they should not track the failed satellite this can bring the time of a loss of integrity alert from a potential 3 hours down to just 6 seconds this is far more acceptable for precision approaches etcsignal availability can also be improved as the sbas transmits ranging signals from its satellites on top of its other roles it acts as an extra gnss satellite

Question 225-14 : In an aircraft based augmentation system abas the method of integrity monitoring that only uses information from the gnss is called ?

Receiver autonomous integrity monitoring raim .

The term aircraft based augmentation system abas covers both aaim aircraft autonomous integrity monitoring and raim receiver autonomous integrity monitoring aaim is a method of monitoring the integrity of the gnss position data using information from on board sensors such as barometric altitude data irs position data and potentially even conventional nav aid autotuning vor dme position data this can allow our aircraft to notice any suspicious gnss position data and notify the pilots that it may not be correctraim is a system which uses extra gnss satellites to effectively verify the working order of the usual 4 required for a 3d position fix 1 extra satellite 5 in total can give the ability to notice when a fault occurs fault detection 2 extra satellites 6 in total gives the ability to detect and identify which satellite is faulty fault detection and exclusion

Question 225-15 : Which statement correctly describes the principle of sbas operation a correction signal is broadcast from ?

Geostationary satellites to gnss receivers distributed over a wide area.

Satellite based augmentation systems sbas sbas uses the idea of differential gps dgps and spreads it over a much wider area than gbas can do their geosynchronous orbits mean that they stay over the same place on the earth all the time and can reduce gnss errors and increase integrity over a very large area this means that there are multiple around the world waas for the usa egnos for europe gagan for india msas for japan etcaccuracy is enhanced through the transmission of wide area corrections for gnss range errors such as ephemeris satellite clock errors and ionospheric propagation sbas systems include reference stations which are geographically distributed throughout the sbas service area which receive gnss signals and forward them to the master station since the locations of the reference stations are accurately known the master station can accurately calculate corrections to each gnss satellite's pseudo range these corrections can then be used to refine gnss measurements over huge areas via the geostationary satellites above those areasgeostationary satellites are those that orbit exactly once every day meaning that they stay over the same point on earth to do this they also have to be over the equatorsbas can be used to make aircraft gnss systems far more accurate on approaches and massively increase integrity monitoring to allow for lower minimums on instrument approaches using this system they are able to give vertical guidance on approaches also similar to the role of baro vnav on lnavvnav approaches they can even be used to refine the gnss signal for lpv approaches localiser performance with vertical guidance which have decision heights as low as 200ft

Question 225-16 : Which of the following correctly describes the principle of receiver autonomous integrity monitoring raim ?

Requires at least five satellites with good geometry to provide the service of detecting faulty signals and alerting the crew.

Receiver autonomous integrity monitoring raim uses redundant signals to produce multiple gps position fixes compare them and detect the faults with redundant gps systemsraim only works with a minimum of five satellites and if sufficient geometry is visible to it raim availability is very important when using the geometry for safety ciritical applications availability is a function of the geometry and other environmental conditions

Question 225-17 : Which statement about dilution of precision is correct the value of the dilution of precision depends upon the ?

Geometry and the number of satellites in view.

Refer to figuredilution of precision dop dop error may be caused by the relative positions of the satellites used to calculate a position to get a better understanding the concept of geometrical dop gdop is often used poor gdop values mean 'bad' positioning of satellites on the contrary 'well' distributed satellites produce good values satellites that are closer together will greate a less accurate position measurement due to the shallow angle difference between their pseudo range spheres whereas satellites which are well spread around the sky will give a more accurate position of the receiver as the pseudo range spheres cut each other at better angles

Question 225-18 : 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.

Satellite based augmentation systems sbas sbas uses the idea of differential gps dgps and spreads it over a much wider area than gbas can do their geosynchronous orbits mean that they stay over the same place on the earth all the time and can reduce gnss errors and increase integrity over a very large area this means that there are multiple around the world waas for the usa egnos for europe gagan for india msas for japan etcaccuracy is enhanced through the transmission of wide area corrections for gnss range errors such as ephemeris satellite clock errors and ionospheric propagation sbas systems include reference stations which are geographically distributed throughout the sbas service area which receive gnss signals and forward them to the master station since the locations of the reference stations are accurately known the master station can accurately calculate corrections to each gnss satellite's pseudo range these corrections can then be used to refine gnss measurements over huge areas via the geostationary satellites above those areasgeostationary satellites are those that orbit exactly once every day meaning that they stay over the same point on earth to do this they also have to be over the equatorsbas can be used to make aircraft gnss systems far more accurate on approaches and massively increase integrity monitoring to allow for lower minimums on instrument approaches using this system they are able to give vertical guidance on approaches also similar to the role of baro vnav on lnavvnav approaches they can even be used to refine the gnss signal for lpv approaches localiser performance with vertical guidance which have decision heights as low as 200ft

Question 225-19 : The system capable of on the ground measuring the signal errors transmitted by gnss satellites and relaying the measured errors to the user for receiver correction is ?

Gbas.

This question is quite badly worded but it is asking which system allows ground receivers to measure calculate and directly transmit those errors to the local receiversthis is referring to gbas ground based augmentation system gbas is a system that attempts to reduce the natural errors within the gnss system by providing very localised augmentation to the satellite signals via a direct vhf data broadcast vdb that a suitably equipped aircraft can receive and use to fix any position errorsit is also called differential gps and can correct for errors induced by satellite clocks ephemeris and ionospheric propagation to make the augmented gnss signal very accuratethese are measurable errors which are measured by multiple receiver antennas and interpreted by a ground station usually located at an airport which can make use of this highly accurate gnsserrors in the receiver multipath signals and some small atmospheric propagation errors can still occur but the intention is to get the accuracy below 1m for aircraft on final approachthe gbas can also like its satellite based cousin sbas give integrity warnings about faulty satellites as it should be able to detect this at the nearby antennasgbas is limited in the fact that it is very short range spanning approximately 30km away from the relevant ground station although it is incredibly accurate and used for complex approaches down to ils minimums and lower minimums in the future is very much possible

Question 225-20 : Which statement about a satellite based augmentation system sbas is correct ?

Sbas is able to provide guidance for precision approaches.

Refer to figure it is the new approach classifications which we think the examiners may have started to use note with recent changes to the regulations we are looking for any exam feedback to verify the question and options thank you rnp approach rnp apch rnp apch can be performed in 3 different ways to 3 different minima lnav only is a non precision approach similar to a vor approach using gnss lnavvnav uses gnss plus a barometric vnav or sbas system to give vertical guidance on the approach and is a 3 dimensional 3d approach with lower minimums than lnav only lpv minimums are even lower as low as 200ft ils cat i due to the narrowing effect of the allowed track like a localiser and the incredibly accurate position data and integrity is gained by using sbas augmentation to the gnss signal it is also a 3d approach standard with vertical guidancesbas cat i approaches are precision approaches according to the more recent documents from icao we are currently unsure as whether the examiners have caught up with these changes so be on the lookout for the older questions which refer to lpv approaches as apv approach with vertical guidance classification into precision and non precision approaches is no longer operationally useful in the current age instead it is better to use 2d and 3d sbas satellite based augmentation system operations use an extra geostationary satellite and a wide network of ground antennas with a master station to calculate the signal errors of gnss location data then apply a correction depending on the user's location to reduce measurable gnss errors to a very small error margin they also increase integrity monitoring so an alert of any unsuitability is issued within 6 secondscommonly confused is the gbas landing system gls which is actually not a form of rnp apch and is a separate type of precision approach that just happens to use ground based augmentation on gnss signals a localised version of sbas

Question 225-21 : How does the gbas precision approach work ?

A gbas ground station sends correction data to the aircraft which uses the data to determine the correct azimuth and glidepath.

Gbas ground based augmentation system gbas is a system that attempts to reduce the natural errors within the gnss system by providing very localised augmentation to the satellite signals via a vhf data broadcast vdb that a suitably equipped aircraft can receive and use to fix any position errorsit is also called differential gps and can correct for errors induced by satellite clocks ephemeris and ionospheric propagation to make the augmented gnss signal very accuratethese are measurable errors which are measured by multiple receiver antennas then interpreted and distributed by a ground station via a vdb antenna usually located at an airport which can make use of this highly accurate gnssthere are still some errors that cannot be accounted for but these are smallgbas also provides integrity information about the gnss satellitesthe operation of gbas allows it to work in the same way as an ils approach down to 200ft minimums currently and this is called the gbas landing system or gls and is a precision approachit is tuned using a 5 digit channel number that picks up the correct vhf datalink signals for that approachthe vhf datalink called the vdb sends a signal that corrects the gnss position so that the onboard navigation system can guide the aircraft accurately on the approach in both azimuth and glidepathnote for this question the examiner is mostly asking what signals are sent in the vhf data broadcast the correct answer is correction data as this is exactly what the gbas system does it corrects the gnss positionthe gbas system does not send glidepath and azimuth data to the aircraft like an ils or mls wouldthis is the primary objective of this questionthe gbas ground station does not tell the aircraft that it is 2 m right and 4 ft above the correct position it tells it to adjust its gnss position by a certain amount then the aircraft makes sure it follows the approach correctlyit also does not matter whether the vdb antenna is classed as part of the ground station or not that is not the defining difference in this questionthe ground station transmits vdb signals via the antenna to the aircraft which still means that the ground station sends signals to the aircraft

Question 225-22 : What does abas stand for ?

Aircraft based augmentation systems.

Abas aircraft based augmentation systemgbas ground based augmentation system sbas satellite based augmentation system aircraft based augmentation system abas the aircraft based augmentation can provide gnss information as necessary for supplemental means of navigationan abas is basically a system that augments andor integrates the information obtained from the other gnss elements with information available on board the aircraft

Question 225-23 : Maximum coverage of a ground based augmentation system gbas station is… ?

20 nm.

Radio navigation 062 learning objectives state that for a gbas station the coverage is about 20 nmground based augmentation system gbas provides its service to a local area approximately a 30 km radius the signal coverage is designed to support the aircraft's transition from en route airspace into and throughout the terminal area airspacenote please take care to notice the unitsnote 2 the old syllabus stated 'state that for a gbas station the coverage is about 30 km'

Question 225-24 : How is the gps receiver able to calculate aircraft's ground speed ?

Using the space vehicle sv doppler frequency shift.

Doppler shiftthe doppler principle can be used to determine the relative speed between moving objects by measuring the difference between transmitted and received frequencies using the space vehicle sv doppler frequency shift andor change in receiver position over time whenever a relative motion exists between the transmitter and the receiver of a radio wave a change in frequency occurs the magnitude of this change is proportional to the relative motion

Question 225-25 : For a satellite to be visible to a gps receiver ?

It needs a higher elevation than 5° above the horizon.

Global navigation satellite systems gnss a satellite will typically be masked from the group of satellites used for position determination until it rised at least 5º above the horizon elevation mask refers to an elevation relative to the horizon in which gpsgnss satellites contained within are not used in a positional solution there is a significant increase in distance between a receiver and a satellite on the edge of the horizon as opposed to a satellite directly above the receiver this increase in distance allows for more ionospheric error resulting in poor accuracy when used in the positional solution

Question 225-26 : Geometric dilution of precision gdop error can be minimized when… ?

One satellite is directly overhead and 3 others are close to the horizon 120 degrees apart.

Refer to figures gdop geometric dilution of precision describes the error caused by the relative position of the gps satellites basically the more signals a gps receiver can see spread apart versus close together the more precise it can be the geometry that will provide the most accurate fixing information is one satellite directly overhead the receiver and the other three close to the horizon and spaced 120 degrees apart in azimuth

Question 225-27 : Referring to the navstargps satellite navigation system what is the meaning of the term receiver autonomous integrity monitoring raim ?

Question 225-28 : You are flying at high latitude and you are unable to identify your position which of the following should you use as back up ?

Irs and barometric altimeter.

Aaim uses additional on board sensors to cross check the gnss position the aaim compares the 3d position with navigation information from on board systems and not with signals from other satellites the navigation systems on board may be self contained inertial reference system irs or radio signals from navigation aids furthermore redundancy to satellite signals may be offered by the barometric altimeter as a back up for positioning in the vertical dimensionnote this question has been created based on incomplete feedback we would kindly ask that you report it to us if you have any further info on this question

Question 225-29 : What is the name of a main chinese gnss system ?

Beidou.

There are four main gnsss these are usa navigation system with timing and ranging global positioning system navstar gps russian global navigation satellite system glonass european galileo under construction chinese beidou under construction

Question 225-30 : Which of the follwing codes can an unauthorized aircraft read ?

Question 225-31 : Which system is capable of measuring on the ground the signal errors transmitted by gnss satellites and transmitting differential corrections and integrity messages to navigation satellites ?

Question 225-32 : What does the term 'sbas' stand for ?

Satellite based augmentation system.

Satellite based augmentation systems sbas sbas operates on the principle of sending navigation correction information to satellites based on actual measurements of signal errors on the ground the signals transmitted by the gnss satellite constellation are transferred to a central computing centre and monitored by ground station and integrity is assessed differential corrections are then transmitted as part of integrity messages within the navigation messages

Question 225-33 : What is the minimum ground based augmentation system gbas plan coverage ?

15 nm from the landing threshold within 35° apart the final approach path and 10° apart between 15 and 20 nm.

Refer to figureground base augmentation systems gbas the basic principle of gbas is to measure the errors of the gnss satellite signals and to relay these errors to the user receiversthe average gbas coverage must be adequate to provide precise augmentation to an aerodrome terminal area the approximate coverage of the dgps antenna is 30 40 km gbas corrects the gps signal to approx+ 4 m vertically and + 16 m horizontallygbas coverage from the leading threshold to enable precise approach navigation is + 35º along the centreline within 15 nm + 10º between 15 nm and 20 nm

Question 225-34 : In the global navigation satellite system gnss what is the user equivalent range error uere it is a computed value for ?

Question 225-35 : In the navstar gps system what can authorised users calculate positions from ?

Pps as well as the less accurate sps.

There are two modes of operation of navstar gps each with a different accuracy the standard positioning service sps is available for civilian users the precise position service pps is only available for authorised users such as the military pps provides a higher accuracy than spsl1 at 1575 mhz provides sps and is used by civilian and military users transmits both ca and p codes l2 at 1227 mhz provides pps and is used by authorized users military transmits p codes

Question 225-36 : An estimate of the position accuracy from the global navigation satellite system gnss can be derived from several factors including ?

Geometric dilution of precision gdop and user equivalent range error uere .

The user equivalent range error uere is the maximum position error that has to be expected by the user and can be calculated as the square root of the sum of all individual errors squared ionospheric propagation delay satellite clock error satellite orbital variations multipath propagation uere is therefore the value of all residual errors affecting the receiver position after attempts have been made to compensatethe actual position error to be expected is however not only affected by uere another factor is the geometric dilution of position gdop the total position error can be computed by multiplying uere by gdop

Question 225-37 : Amongst others sbas allows for the implementation of ?

Question 225-38 : An aircraft flying out of sight of land using gnss and abas without sbas briefly loses power to the irs the navigation information of the irs is lost due to the temporary power loss what effect could this failure have on how gnss is used during the flight ?

Reducing abas to raim and barometric altitude only.

Airborne based augmentation system abas is a type of augmentation system that is installed on board aircraft abas has two sub categories receiver autonomous integrity monitoring raim and aircraft autonomous integrity monitoring aaim therefore abas = raim + aaim raim improves redundancy based only on multiple satellite signals and no external systems it applies the technique of using more satellites in view than the minimum 4 that are needed for a 3d position fix this method is using to verify the fixing information aaim uses additional on board sensors such as barometric altimeter and inertial reference system to cross check the gnss position it compares the 3d position with the navigation information from on board systems and not with signals from other satellites => if the inertial reference system irs is lost barometric altitude from aaim and the raim function are still available

Question 225-39 : The accuracy of the navstar gps position depends on the geometry of the intersecting lines select the correct statement ?

If the satellites as viewed by the gps receiver are close together there will be a poor angle of intersection resulting in a loss of accuracy.

Refer to figureposition dilution of precision pdop is an error resulting from adverse positioning of satellites and the number of satellites in view for gps it is important that satellite defined spherical surface positions are such that they do not degrade the potential accuracy of the resultant fix if the satellites lie too close to each other it results in a poor intersection of the spherical surfaces for a good intersection the ideal arrangement to ensure adequate spacing is one satellite directly above and the other three close to the horizon space at 120º from each other

Question 225-40 : If a gps malfunction occurs egnos provides an alert time within ?

6 seconds.

Los reference 06206020209 explain that integrity and safety are improved by alerting sbas users within 6 seconds if a gps malfunction occursthe european sbas is called egnos and was developed by the european space agency its primary purpose is to check the accuracy and reliability of gnss positioning and to send out corrections whenever necessary egnos supports integrity and safety by alerting users within 6 seconds if a satellite malfunctions occurs gps alone is only capable of alerting within 3 hours