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14 Pseudo-Ranging Radio Navigation Systems
The crew activates the operation of the onboard GNSS equipment in differential
mode (mode of operation with LCCS) and selects a precision approach scheme using
LCCS, which is provided by the onboard equipment channel number switch. A GBAS
precision approach is performed by the method much like ILS precision approach,
using lateral guidance in an intermediate segment prior to entering the glide path,
after which vertical guidance begins and continues to be provided along with lateral
guidance for landing. The minimum required functionality for displaying information
from the LCCS in the AV cockpit is equivalent to the information displayed during
an ILS approach. LCCS continuously provides the necessary information, on the
basis of which the onboard equipment calculates the deviation from the given track
line and in automatic (under control by the aircrew) or manual mode this deviation
is compensated.
GBAS ground station failure information display and alarms are similar to ILS
approach information. Along with signaling about failure, the LCCS constantly
provides information on the integrity of the procedure in automatic mode. If the
onboard equipment provides information about the impossibility of continuing the
operation due to the LCCS failure or the impossibility of performing the intended
operation using GNSS, the crew must immediately stop the operation and, together
with the ATC controller, take measures to safely continue the flight.
To date, five wide-area differential correction systems have been presented:
• WAAS—wide-area system of functional additions, USA;
• WDCMS—wide-area differential correction and monitoring system, Russia;
• EGNOS—European Geostationary Navigation Service, EU;
• GAGAS—geostationary navigation supplement of the GPS, India;
• MSAS—Space Augmentation System, Japan.
There are proprietary global differential correction systems such as the StarFire
navigation system (a commercial John Deere company system); Starfix DGPS and
OmniSTAR (commercial system of Dutch Fugro N.V. company).
A separate place among the global differential correction systems is for the “PPP
service” (Precise Point Positioning—high-precision absolute positioning). PPP technology is capable of providing positioning accuracy from decimeter to centimeter
or more (for static mode) when combining accurate satellite orbits and clocks with
a dual-frequency GNSS receiver (by taking into account the effect of the first-order
ionosphere).
The main advantages of PPP technology over other differential positioning
methods include the fact that only one receiver is necessary for PPP realization
and no special base stations are required in the close vicinity of the user.
It is necessary to specially highlight functional supplement that differ from those
traditionally used by users—pseudo-satellite and assisting functional augmentations.
Pseudo-satellite functional augmentations are one or more pseudo-satellites
(navigation satellites located on the ground) that generate navigation signals in the
GNSS format. They complement the GNSS global radio navigation field in a given
area and usually have a local operating zone. Its size is determined by the power of
the transmitter of the pseudo-satellites and the line-of-sight range.
14 Pseudo-Ranging Radio Navigation Systems
The crew activates the operation of the onboard GNSS equipment in differential
mode (mode of operation with LCCS) and selects a precision approach scheme using
LCCS, which is provided by the onboard equipment channel number switch. A GBAS
precision approach is performed by the method much like ILS precision approach,
using lateral guidance in an intermediate segment prior to entering the glide path,
after which vertical guidance begins and continues to be provided along with lateral
guidance for landing. The minimum required functionality for displaying information
from the LCCS in the AV cockpit is equivalent to the information displayed during
an ILS approach. LCCS continuously provides the necessary information, on the
basis of which the onboard equipment calculates the deviation from the given track
line and in automatic (under control by the aircrew) or manual mode this deviation
is compensated.
GBAS ground station failure information display and alarms are similar to ILS
approach information. Along with signaling about failure, the LCCS constantly
provides information on the integrity of the procedure in automatic mode. If the
onboard equipment provides information about the impossibility of continuing the
operation due to the LCCS failure or the impossibility of performing the intended
operation using GNSS, the crew must immediately stop the operation and, together
with the ATC controller, take measures to safely continue the flight.
To date, five wide-area differential correction systems have been presented:
• WAAS—wide-area system of functional additions, USA;
• WDCMS—wide-area differential correction and monitoring system, Russia;
• EGNOS—European Geostationary Navigation Service, EU;
• GAGAS—geostationary navigation supplement of the GPS, India;
• MSAS—Space Augmentation System, Japan.
There are proprietary global differential correction systems such as the StarFire
navigation system (a commercial John Deere company system); Starfix DGPS and
OmniSTAR (commercial system of Dutch Fugro N.V. company).
A separate place among the global differential correction systems is for the “PPP
service” (Precise Point Positioning—high-precision absolute positioning). PPP technology is capable of providing positioning accuracy from decimeter to centimeter
or more (for static mode) when combining accurate satellite orbits and clocks with
a dual-frequency GNSS receiver (by taking into account the effect of the first-order
ionosphere).
The main advantages of PPP technology over other differential positioning
methods include the fact that only one receiver is necessary for PPP realization
and no special base stations are required in the close vicinity of the user.
It is necessary to specially highlight functional supplement that differ from those
traditionally used by users—pseudo-satellite and assisting functional augmentations.
Pseudo-satellite functional augmentations are one or more pseudo-satellites
(navigation satellites located on the ground) that generate navigation signals in the
GNSS format. They complement the GNSS global radio navigation field in a given
area and usually have a local operating zone. Its size is determined by the power of
the transmitter of the pseudo-satellites and the line-of-sight range.