22 Different PNT data processing functions need comprehensive input data to keep the
PNT-DP running as specified in this document. These Guidelines define how the
shipborne PNT-DP should provide output data by processing input data (from sensors
and/or services and/or sources) while availability and performance of input data may
vary temporally and spatially (see figure 4).
Figure 4: Sensors, services, and sources
23 The desired level of PNT data output depends on currently available inputs that
may independently vary over a short or long period of time. These Guidelines aim to
specify the demand on needed types of services, sensors, and sources for predefined
performance levels of PNT/I data (module B).
24 These Guidelines specify PNT-DP's real-time adjustments of the used
data processing functions (module B and C) to applicable methods taking into account the available
input data.
25 The PNT-DP processes data from type-approved sensors and recognized services.
26 In a minimum configuration, PNT-DP uses the minimum number and type of
sensors as defined in SOLAS (depending on the ship type). The manufacturer may
add inputs and outputs to achieve better performance or more information (e.g. with
integrity indication) at output of PNT-DP to support additional nautical functions
and tasks that require better performance or more information (e.g. with integrity
indication).
27 The necessary sensor, service, and source layout is determined by the necessary
performance of PNT data provision and integrity evaluation for the subsequent
nautical functions and tasks.
A.1 Types of services for positioning
28 Services are classified by grade/type as follows:
-
.1 Radionavigation services provide navigation
signals and data which enable the determination of ships' position,
velocity and time.
-
.2 Augmentation services are other services that
provide additional correction and/or integrity data to enable
improvement of radionavigation-based determination of ships position,
velocity and time.
29 Services are classified regarding its geographical coverage:
-
.1 Global services are characterized by their
worldwide coverage. They may have limitations regarding usability for
different phases of navigation due to signal disturbances reducing the
availability or performance of transmitted signals and/or provided data.
-
.2 Regional services (and maybe local services) are
only available in dedicated service areas. They may be used to improve
the performance of ships' navigational data in terms of accuracy,
integrity, continuity and availability even in demanding operations
when, for example, higher accuracy and integrity level is required
during coast and port navigation.
A.2 Types of sensors and sources
30 The type-approved sensors and data sources are distinguished into the following
categories:
-
.1 Service-dependent sensors rely on any service from
outside the ship provided by human effort. They cannot be used on board
without at least a satellite-based or terrestrial communication link to
the service provider (shown in figure 4, mainly used to provide data of
ships position, velocity and time).
-
.2 Shipborne sensors and sources:
-
.1 Primary sensors use a physical principle,
e.g. earth rotation or water characteristics and are independent
of any human applied service provision (shown in figure 4,
mainly used to provide data of ships attitude and movement);
-
.2 Secondary sensors and sources may be used
to provide additional data for the verification of PNT data (see
figure 4), e.g. water depth at known position from an ENC, line
of position, or directions and distances provided by onboard
RADAR.
31 The above described sensors are considered to be usable worldwide and free of any
rebilling user charge
A.3 Additional input data
32 In addition to sensors, services and sources listed in A.1 and A.2 further
PNT-relevant data may be used for shipborne PNT data provision to increase
redundancy or to evaluate plausibility and consistency of data input (ship sensed
position, e.g. by position reference systems). Such data may be provided via AIS or
VHF Data Exchange System (VDES), see figure 4.
A.4 Requirements on input data
All sensors, services and data sources used as input for the shipborne PNT-DP should
comply with the relevant IMO performance standards.