| GNSS/INS Coupling
Because of different error influences based on space
segment, signal propagation, receiver technology or user environment the
accuracy potential of GNSS systems is not sufficient for all applications
in geodesy and navigation. Additionally the
availability and data frequency
can be inadequate. Therefore many navigation or surveying systems use hybrid
GNSS/INS sensors to combine the only short-time stability of an inertial
sensor and the long-time stability but noise behaviour of a GNSS receiver.
Furthermore both sensors base on completely different principles for the
determination of position, velocity and attitude. Depending on the application
and the used sensor types more or less advantages in accuracy,
availability, integrity
and data frequency can be achieved.
GNSS/INS
systems can be characterized by their implemented coupling principle. Today
basically three different methods are operational or current investigation
topic: loose, tight or deep coupling.
Most GPS/INS
integrations are loosely coupled, giving up a great deal of performance
in return for simplicity of integration. Using this principle the position
and velocity estimates of a GNSS receiver are used as observations in an
INS filter for estimation
of INS errors, a reduction of GPS-noise and a bridging of GPS outages are
possible
 Loose coupling
principle
In this case the GNSS
measurements are also usable when fewer than four satellites are tracked.
Knowing the INS position lost ambiguity values can be restored more
quickly.
In case of high
dynamic applications or in jamming environments the principle of
tight-coupling becomes very interesting. Information about the receicer
dynamics measured by the inertial sensor is used to support the tracking
loops of the integrated navigation system.
Tight coupling
principle
An extension
of this concept is the deeply coupling method. In this case the
integrating navigation filter is implemented as one element of the receiver
tracking loop. Using inertial information in combination with the in-phase
and quadra-phase signals of the receiver signal processing an optimal controlling
value for the numerical oscillator can be computed. Optimisations of signal
tracking performance are the goal of this method.
Sensor Components
GNSS/INS
Applications
Point
of contact: Prof. Bernd Eissfeller |
