RNAV | Long Range Systems Flashcards
Theses are systems which don’t rely on __ range navaids
short
INS is a ___ range nav system
long
The two current GNSS are ___ and ___
NAVSTAR/GPS and GLONASS
Satellites have ___ clocks on board
atomic
To attain an altitude reading from GPS, _ sats are required
4
GNSS reliability approaches 100% within 100m of the horizontal for __% of the time, and 300m for __% of the time.
95 99
GPS accuracy can be affected by ___, ___, and ___
Atmospheric interference, sat positioning, turning inaccuracies
Each satellite has 3 sections:
- Timing
- Signal Generation
- Transmitting
Galileo uses two types of clock, ___ and ___
Rubidium Frequency standard clock, passive hydrogen master
Galileo should use __ sats in total, with _ and _ spare in each of _ planes.
30 9 1 3
Galieo’s orbit is at an altitude of ___km
23222
Galileo’s orbit is inclined __ degrees to the Equator
53
Galileo’s orbit takes __ hours
14
Galileo’s signals are transmitted on the bands ___
- 1164-1215 MHz
- 1260 - 1300 MHz
- 1559-1592 MHz
NAVSTAR uses __ satellites, + _, in _ groups of _
21 3 6 4
NAVSTAR sats are __ degrees apart
60
NAVSTAR aims to have __ satellites operational at any one time
21
The NAVSTAR receiving frequency is ___ _Hz
1575.42 MHz
NAVSTAR sats orbit in _ circular planes, _____ km above the Earth, with _ in each plane
6 20200 4
Each NAVSTAR sat should have a __ degree view of the Earth, at least _ should be in line of sight from any point on the Earth
28, 5
Satellites are in view when they are _ degrees above the horizon
5
A good combination for GPS reception is _ with a low elevation, with a ___ degree spread, with a _ directly overhead.
3 120 4
When a satellite is going North to South, it is in the __ node
ascending
The mask angle is the ___ angle above the horizon at which the sat can be used
lowest
A sat’s inclination is the angle between the ___ and ___ plane
orbital, Equatorial
NAVSTAR satellites move once around the Earth from _ to _ once every __ hours and __ minutes
W E 11 58
NAVSTAR sat transmitting power is about __ Watts
50
The NAVSTAR system consists of 3 segments:
Space, Control, User.
The NAVSTAR space segment consists of ___
satellites
The NAVSTAR control segment consists of ___
- Master control station
- 5 monitoring stations
- Ground antenna
The purpose of the NAVSTAR control segment is to ____
- Manage performance
- Upload nav data
- Monitor sats
The NAVSTAR user segment consists of ___
receivers
In the NAVSTAR user segment, single channel receivers move ___
from one satellite to another in sequence
In the NAVSTAR user segment, multi channel receivers ___
continuously monitor position data whilst locking onto other satellites
In the NAVSTAR user segment, continuous receivers have up to __ channels, and can eliminate GDOP problems by watching up to _ sats
12 4
For NAVSTAR, the receiver antenna are ___-___, with the active element being a quarter wavelength of . _Hz; 2.5 cm
semi-omnidirectional, 1.6 GHz
The satellite transmits a signal composed of a digital code, modulated on a ___ carrier frequency known as 1.1, whose timing is controlled by an ___ clock.
microwave, atomic
A GPS receiver can tune into a satellite by generating its own copy of the ___ code and carrier, matching their timings to the incoming signal; the differences are converted into a distance.
Gold
Satellites transmit a ___ ___ code, in which a nav data message is encoded.
Coarse Acquisition
The CA code is a ___ bit PRN transmitted at _.___ Mbits/second, repeated every millisecond.
1023, 1.023
The ___ of each satellite is known by the receiver, which can generate them internally.
PRN
Nav data is transmitted every __ seconds as frames, containing _ subframes.
30 5
The 5 subframes contained within the nav data are:
- Clock
- Ephemeris
- Ephemeris
- Almanac
- Almanac
The Ephemeris subframe contains data about the exact orbital path for the next _ hours
4
The Almanac subframe contains ___ precise positioning details
less
Time runs ___ slowly with ___ gravity
more more
The sat signal is modulated with ___
pseudo-random numbers.
Almanac information is transmitted every __._ minutes, taking __._ minutes to download
12.5 12.5
The Almanac data covers ___
- Sats operating normally
- PRN codes of available sats
- Predicted positions of sats in their orbits.
Each satellite transmits its own ephemeris data, every __ seconds and taking __ seconds to download. The data is valid for _ to _ hours.
30 12 4
For NAVSTAR, two _HF frequencies are used:
- L1, ___ _HZ
- L2 ___ _Hz
Both frequencies are multiples of a base frequency, 10.23 _Hz
1575.42 MHz
1227.60 MHz
MHz
GLONASS uses _ planes, with _ satellites, equally displaced by __ degrees of latitude
3 8 45
GLONASS sats fly at ___ km, at an inclination of __._ degrees
19100 64.8
Each GLONASS orbit takes __ hours __ minutes
11 15
GLONASAS signals are transmitted on the _ band, which is _HF,
L UHF
GLONASS L1 is . _Hz, and L2 is . _Hz
1.6 GHz, 1.2 GHz
The majority of PBN operations can be conducted using ____ satellite systems
unaugmented
GBAS is the practical application of ___ ___ ___ GPS
Local Area Differential
GBAS uses a ___ signal from a precisely surveyed ground based transmitter, whose position can be compared against that of the receiver.
5th
GBAS corrections are sent directly to aircraft receivers form ground stations at airports, within __-__nm
20 30
The GBAS ground station signal is able to provide ___ and ___ data
error correction integrity
GBAS coverage is within ___ of the final approach, up to 15 nm away from the landing threshold, _ degrees within 15-20 nm.
35 10
GBAS + GPS is called ____ in the US
Local Area Augmentation System
In summary, GBAS can provide ___
- Precision approach down to 200ft
- Horizontal positioning for RNAV in terminal areas
SBAS is used to extended ___ GPS to a larger area
differential
SBAS works on the principle of measuring the signal errors from satellites and providing separate corrections for ___, __, __, and ___ errors.
ranging, ephemeris, clock, ionospheric
With SBAS, correction data is transmitted to ___ satellites, and then re-transmitted to the ___
geostationary user
SBAS regionally augments ___ and ___ by making them suitable for safety-critical procedures.
GPS, GLONASS
WAAS, standing for ___, allows GPS to be used through flight, including a Cat _ precision approach.
Wide Area Augmentation System, Cat I
With WAAS, sat signals are received by ___, which detect errors and send them to a ___, which adds correction information based on ___, and sends the connection message to ___ for rebroadcast.
precisely surveyed ground stations, master station, geographical area, geostationary satellites
LPV stands for ____
Lateral Precision with Vertical Guidance
SBAS guidance is (not) subject to altimeter errors
not
With SBAS being used, the additional satellites which would be used for ____ are not required as the messages are available wherever the sat signal can be received.
RAIM
WAAS uses two satellites over the ___ and ___
Atlantic and Pacific
EGNOS is the ___
European Geostationary Navigation Overlay Service
EGNOS as the European equivalent to ___
WAAS
EGNOS coverage is limited to between __N and __S, which is ___ North then WAAS
80 80 further
EGNOS can improve accuracy to _ to _ m horizontally, and _ to _ m vertically
1 2 3 5
EGNOS allows users to be alerted of malfunctions within _ seconds, rather than _ hours
6 3
ABAS uses ___ to develop integrity control
excess information within the GNSS constellation
ABAS does (not) improve positioning accuracy, unlike GBAS/SBAS
not
ABAS which uses GNSS information only is ___
RAIM
A system using information from additional on board sensors is called ___
AAIM
RAIM helps to detect and correct faults more quickly than the standard ____
2 hours
RAIM is achieved within the ___, which monitors satellites and verifies their signals.
receiver
An ___ ___ is required for RAIM
extra satellite
Basic RAIM needs _ satellites to work, and _ to continue working with one having failed
5 6
With RAIM available, the integrity limits are: _ nm for oceanic _ nm for enroute _ nm for terminal _._ nm for GPS approaches.
4
2
1
0.3
With RAIM unavailable, GPS must be ____
integrated with other systems
RAIM can be assisted with baroaiding, this ___ the number of satellites required.
reduces
Clock coasting uses the atomic clocks in the ___ segment to reduce clock bias
user
GNSS errors are smallest when satellites are ___
overhead
When a receiver starts, its own clock is inaccurate by an unknown error called ___ ___ .
clock bias
Clock bias is correct in the receiver by running ____ ____
simultaneous equations
Satellites heading towards the sun ___, and those away ___, causing satellite clock drift. This is the largest unmeasureale source of error.
decelerate
Accelerate
Ephemeris error it the result of the satellite ____
not being where it thinks it is
Ephemeris error can arise as a result of ___ effects
gravitational
Ground monitoring stations check satellites every __ hours, with the maximum error being . metres
12 2.5
UHF signals are (not) normally refractable in the ionosphere
not
The small amount of refraction which UHF signals do suffer in the ionosphere makes signals travel ___ than they should
further
The sat signal __ as it passes through the ion layers
attenuates
The error caused by refraction is called ___ ____ ____ and produces an error of around __m
ionospheric group delay, 5m
Ionospheric group delay is ___ proportional to the square of the frequency
inversely
Ionospheric propagation is the ___ natural error
worst
Internal noise within circuits can cause positioning errors of up to _ m
0.3
Water vapour in the troposphere will affect ___
refraction
The maximum error from tropospheric propagation is between _m and _m
0.3 0.5
Multipath reflection occurs as a result of ___
the antenna being shadowed by parts of the aircraft, and preventing signals being transmitted/received
The maximum multipath reflection error is _m
0.6
C/A Selective Authority used to be done by ___ satellite clocks
dithering
Manoeuvring errors are caused by ___
aircraft attitudes
GDOP/PDOP stands for ___
Geometric or Position Dilution of Position
GDOP can occur when satellites are ___ ___ to one another, downgrading their accuracy
too close
A GDOP of less than __ is required for enroute nav, and less than _ for precision approaches.
6 3
Normal accuracy of 100m for 95% of the time assumes a PDOP of _, and a range error of __m
3 33.3
Range errors are multiplied by PDOP to obtain ___ ___
stated accuracies
GDOP is ___ by RAIM
minimised
Search the Sky is a procedure which starts___
after switching on the receiver if there is no stored satellite data available
The closer the receiver is to a LAAS ground reference station, the ____ accurate the fix
more
The data elements transmitted by NAVSTAR GPS satellites include:
- Offset of sat clock from UTC
- Ephemeris data
- Satellite health status data
- Ionospheric delays
The Galileo navigation messages contains ___
information about the satellite orbit and clock references
Satellites transmit on _HF
UHF
