218
4 Navigations from Ground to Space
Fig. 4.4 Principle diagram of TACAN
radio landing guidance system provides accurate guidance information for aircrafts,
such as landing orientation, glide path and distance. Thereby, the aircraft aligns the
runway according to the guidance information, and approaches and lands according
to the given glide angle to ensure that the deviation of the ground point is within
the specified range. Generally, the landing guidance system is divided into three
types, such as Instrument Landing System (ILS), Ground Control Approach System
(GCAS) and Microwave Landing System (MLS).
4.5.2 Hyperbolic Navigation System
The hyperbolic navigation system is a kind of radio navigation system which by
taking the ranging differences as the basic observables uses the intersection of hyperbolic position lines to realize positioning for movable objects. Its basic principle is:
when the differences between the distances from each point along the trajectory of
a movable object to two fixed points are constant, this trajectory is a hyperbola with
the two fixed points as the focal points. When there are two hyperbolas intersected in
a plane, the intersected point can be positioned. The hyperbolic navigation principle
of offshore ship is shown in Fig. 4.5, where P is the ship’s position to be determined,
A is a major station, both B and C are the sub-stations, and the three stations are
deployed in the fixed shore sites and marked in a nautical chart. Given the distance
values of AC and AB, when both the distance difference d1 between BP and AP and
the distance difference d2 between CP and AP are measured, two hyperbolas can
be drawn in the nautical chart by taking A and B as the first focus pair, A and C as
4 Navigations from Ground to Space
Fig. 4.4 Principle diagram of TACAN
radio landing guidance system provides accurate guidance information for aircrafts,
such as landing orientation, glide path and distance. Thereby, the aircraft aligns the
runway according to the guidance information, and approaches and lands according
to the given glide angle to ensure that the deviation of the ground point is within
the specified range. Generally, the landing guidance system is divided into three
types, such as Instrument Landing System (ILS), Ground Control Approach System
(GCAS) and Microwave Landing System (MLS).
4.5.2 Hyperbolic Navigation System
The hyperbolic navigation system is a kind of radio navigation system which by
taking the ranging differences as the basic observables uses the intersection of hyperbolic position lines to realize positioning for movable objects. Its basic principle is:
when the differences between the distances from each point along the trajectory of
a movable object to two fixed points are constant, this trajectory is a hyperbola with
the two fixed points as the focal points. When there are two hyperbolas intersected in
a plane, the intersected point can be positioned. The hyperbolic navigation principle
of offshore ship is shown in Fig. 4.5, where P is the ship’s position to be determined,
A is a major station, both B and C are the sub-stations, and the three stations are
deployed in the fixed shore sites and marked in a nautical chart. Given the distance
values of AC and AB, when both the distance difference d1 between BP and AP and
the distance difference d2 between CP and AP are measured, two hyperbolas can
be drawn in the nautical chart by taking A and B as the first focus pair, A and C as