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RNAV 2 (Weather Radar - Ch 9 CTB has all the Qs that are typical of exams…

- - - - Weather + Turbulence Mode (WX+T)
        
        Uses doppler to detect areas of turbulence - shown magenta
        * Has a 40nm limit
      - Map Mode i.e. using WX radar to map the ground
        
        Black = Water
        
        Green = Land
        
        Amber = High ground or large settlements and cities
        
        In mapping mode, the radar can see coastlines, hills/mountains and larger settlements.
        Note: you cannot display terrain and WX together*
      - Weather Mode (WX) - think reverse traffic light
        
        Black = No or very little precipitation and very small water droplets.
        
        Green = Light precipitation and small size droplets giving light turbulence.
        
        Amber = Medium precipitation and medium size droplets giving medium turbulence.
        
        Red = Heavy precipitation and large size droplets giving medium to severe turbulence.
        
        Magenta = Beyond red giving severe turbulence
- - - - 2 Interrogation modes:
        
        All - Call transmitted regularly at intervals
        
        Selective Call - 'on demand' - EXAM: ‘locked out’ ‘decluttered’ so they can’t see you
        -
        
        AC will respond and send actual speed, heading and altitude
        
        But also: selected speed, heading, altitude and altimeter setting
      - ELS - Elementary Surveillance
        
        ELS provides AC position, alt and ID.
        
        Within European Mode S airspace, aircraft intending to fly IFR as GAT must be ELS compliant and provide the following “Basic Functionality”:
        AC ID, Alt in 25 ft intervals, status (airborne or on grnd), SI code capability
      - EHS - Ehanced Surveillance
        
        AC TOM > 5700kg or max cruise TAS> 250kts , intending to fly IFR as General Air Traffic (GAT) , must be Mode S EHS compliant and provide the following:
        most nav parameters: IAS, Mach, *NOT TAS, Alt, selected alt, mag and true headings and tracks...
      - Mode S interrogators and transponders communicate with each other using a data-link system.
        
        Comm A to D...check if ELS is CommB
      - SPI (special position identification) transmits an Ident signal for 20 seconds when the pilot is instructed to ‘squawk Ident’.
- - - - Principle of operation
        
        Sats broadcast ranging codes & time
        
        Rcvr measures signal transmission time to determine range
        
        4 sats used, 4th corrects timing error
        
        Timing error always exists - Resolved by keeping receiver clocks a little slow so that range is always over-estimate
        
        initial calculated ranges are known as “pseudo ranges”
        
        WGS-84 ellipsoid
        
        GPS Time
        
        2 modes:
        STANDARD POSITIONING SERVICE (SPS) for civilian users
        PRECISE POSITIONING SERVICE (PPS) for military
      - Space Segment
        
        24 operational satellites
        
        6 Orbits ( 4 satellites in each)
        
        Average orbit height - 20,200km
        
        Orbit inclination = 55deg to Eqautor
        
        Orbit time - 12 hrs
        
        5-8 satellites observable at any time
        
        THEY ARE NOT GEOSTATIONARY
        
        Link 1(L1) on 1575.42MHz
        
        Link2(L2) on 1227.6MHz
        
        Freqs & modulations
        
        Link 1 (L1) on 1575.42 MHz.
        ** The L1 signal is modulated with a coarse/acquisition (C/A) modulated code associated with SPS and a precision (P) modulated code associated with PPS
        
        Link 2 (L2) on 1227.6 MHz. The L2 signal contains a precision (P) modulated code only
        .
        
        Both signals contain 3 essential pieces of information:
        
        Pseudo-Random Noise (PRN) code
        
        Time of Transmission (TOT)
        
        Navigation Message (NAV MSG)
        
        Almanac data - approx position info for each SV
        
        Ephemeris data - Precise position info for the SV transmitting
        
        Satellite Clock correction parameters
        
        UTC parameters (convert diff in GPS time to UTC)
        
        Ionospheric model - allows receiver to correct timing issues caused by ionosphere
        
        Sat health data
        
        GPS receiver take 12.5 mins to receive the nav message
        
        GPS Time
        
        GPS time in seconds from 00:00:00 UTC 6 Jan 1980
        
        Diff. wuth U"TC = 19secs
        
        Each satellite has 3 or 4 atomic clocks that keep accurate to 1 nanosecond
      - Control Segment
        
        Tasks
        
        Manage SPS perf
        
        Nav data upload
        
        Monitor Sats
        .
        
        Components
        
        Master Control Station - responsible for all the command and control of the whole system (V IMPORTANT)
        
        Ground Antenna
        
        Monitoring stations
      - User Segment
        
        GPS rcvrs supply:
        
        3D posn fix
        
        Precise time ref.
        
        Speed data
        
        Types of rcvr
        
        Sequential receivers
        
        1 or 2 channels - tracks only 1 SV at a time
        
        Tracks 4 sats then combines pseudo ranges
        
        Multiplex
        
        Same as Sequential but can switch between 4 Sys quickly so calc pseudo ranges quicker
        
        Multi-channel
        
        Receivers all GPS signals at once, in parallel - selects best SVs to perform a fix
        
        This is what we use in aviation. Therefore error reduced
      - Errors and accuracy
        
        Ionospheric error
        
        Ephemeris error
        
        Satellite Clock Error
        
        Multi-path reception
        
        Selective availability (US F**ing with GPS)
        
        A/C manouevring
        
        Geometric Dilution of precision (GDOP) *i.e. sats too close - poor triangulation
        
        GDOP
        
        Optimum geometry for receiver to minimise GDOP = One SV overhead and 3 SVs close to horizon 120deg apart
        
        Comprises:
        
        Position (PDOP)
        
        Horizontal (HDOP)
        
        Vertical (VDOP)
        
        Time (TDOP)
    - - Principle of operation
        
        Same as NAVSTAR...
        
        PZ-90 datum
        
        UTC time
        
        2 modes:
        STANDARD PRECISION (SP) for civilian users
        HIGH PRECISION (HP) for military
      - Space Segment
        
        24 satellites
        
        3 Orbits (8 satellites in each orbit)
        
        Inclined to 64.8 deg
        
        Av. Orbit height 19100km
        
        Av. Orbit completed in 11hr 15mins
        
        Satellites use the PZ-90 datum
        
        THEY ARE NOT GEOSTATIONARY
        
        Link 1(L1) on 1.6GHz
        
        Link2(L2) on 1.2GHz
        
        Freqs & modulations
        
        Link 1 (L1) on 1.6GHz (15 channels)
        
        Link 2 (L2) on 1.2GHz (15 channels)
        .
        
        Nav Message
        
        Include IMMEDIATE and Non-immediate data * Immediate = i.e. time data
        
        Non-immediate data relates to all other satellites within the constellation.
        
        Satellites transmit 2 second nav message every 30 mins
      - Control Segment
        
        Tasks
        
        Manage SPS perf
        
        Nav data upload
        
        Monitor Sats
        .
        
        Components
        
        Located entirely in former soviet union territory
        
        Ground control centre and time standards located in Moscow
      - User Segment
        
        Read NAVSTAR info
        
        Available since 2007
      - Errors and accuracy
        
        See NAVSTAR
      - Integrity
        
        Done on the satellite and on the ground (Ground control centres)
    - - Principle of operation
        
        Same as NAVSTAR...
        
        ETRS89 (European Terrestrial Ref System)
        
        Not yet operational
        
        GMT time
        
        Estimated 1 Jan 2020
      - Space Segment
        
        30 satellites
        
        3 Orbits (10 satellites in each = 9 + 1 spare)
        
        Inclined to 56 deg
        
        Av. Orbit height 23,222km
        
        Av. Orbit completed in 14hrs
        
        EXAM: Each SV has 3 sections:
        Timing section:2 on board atomic clocks : a rubidium freq. standard clock and a very accurate passive hydrogen master clock
        Signal Generation:Message comprise ephemeris and orbit info and clock references
        Transmit section:3 freq bands
        
        3 freq bands
        
        Freqs & modulations
        
        3 freq bands
      - Control Segment
        
        Tasks
        
        Manage SPS perf
        
        Nav data upload
        
        Monitor Sats
        .
        
        Components
        
        2 Galileo Control Centres (GCCs) in Europe
      - User Segment
        
        Read NAVSTAR info
      - Errors and accuracy
        
        See NAVSTAR
      - Integrity
        
        Done on the satellite and on the ground (Ground control centres)
    - - Ground based augmentation system (GBAS)
        
        aka Local Area Differential GPS (LADGPS) aka Loacl Area Aug. System (LAAS) - key is LOCAL AREA
        
        The Precision Approach Service
        
        Psuedolites
        
        Uses GPS signal and calcs corrections
        
        Sends correction info continuously to AC via VHF data link on the ILS/VOR freqs (Freqs BUT DOESN'T NEED ILS/MLS/VOR!)
        
        AC applies the correction to its own GPS position
        
        CAT IIIC capable
        
        +/-35º from centreline within 15 nm
        
        +/-10º from extended centreline within 20 nm
        
        GBAS POSITONing service
        
        Network of psuedolites
        
        Broadcasting large - scale corrections as a Ground Regional Augmentation System (GRAS)
      - Satellite based augmentation system (SBAS)
        
        aka Wide Area Differential GPS (WADGPS)
        
        SBAS is more accurate than Navstar GPS
        
        European Geostationary Navigation Overlay System (EGNOS)
        
        Wide Area Augmentation System (WAAS) operated by US
        
        Multi-function Transport Satellite Augmentation System (MSAS) operated by Japan.
        
        Geo And GPS Augmented Navigation (GAGAN) operated by India
        
        EGNOS
        
        3 Geostationary SV are fed position error corrections from Ground based Control Segment.
        
        These 3 sats then include differential GPS errors as part of their transmission of ID, Time, Nav message.
        
        Space Segment
        
        3 Geo stationary satellites
        
        Control Segment
        
        Ground stations calc the position errors from the constellations (NAVSTAR/GLONASS) an send the correction info to the 3 Geostationary satellites
        
        User Segment
      - Air based Augmentation system (ABAS)
        
        Monitors integrity
        
        Receiver Autonomous Integrity Monitoring (RAIM) i.e. stands alone
        
        Autonomous = standalone, no other signal except GPS rcvd. AC system does all integrity calcs
        
        Basic RAIM - Fault detection only
        
        Adds 5th satellite to 4 used and checks they make sense
        
        Enhanced RAIM - fault and fix
        
        Uses 6th Sat to correct the signal i.e. if 5th says Sat 3 is in error it swaps out the 3rd for the 6th