dk.dma.ais.message

Class AisMessage1

java.lang.Object

dk.dma.ais.message.AisMessage

dk.dma.ais.message.AisPositionMessage

dk.dma.ais.message.AisMessage1

All Implemented Interfaces:

IPositionMessage, IVesselPositionMessage, Serializable

Direct Known Subclasses:

AisMessage2

public class AisMessage1
extends AisPositionMessage

AIS message 1

This class handles the content of an AIS class A transponders general position report as defined by ITU-R M.1371-4.

Generally the position report is handled in the super class but there are some specific purposes of this class. This is mainly the communication state field, that requires some special attention.

The communication state field covers 19 bits and this is general to both message 1, message 2 and message 3. The content is though different for the different communication states applied by the different message types.

This message type is using SOTDMA communication state, which is described below.

CommState - 19 bits sync state: 2 bits slot timeout: 3 bits sub message: 14 bits

The sub message depends upon the value of the slot timeout. The slot timeout is defined to be between 0 and 7 both values included.

The sub message is defined as:

When slot timeout = 0 - Then the sub message is the slot offset: If the slot time-out value is 0 (zero) then the slot offset should indicate the offset to the slot in which transmission will occur during the next frame. If the slot offset is zero, the slot should be de-allocated after transmission

When slot timeout = 1 - Then the sub message is UTC hour and minute: If the station has access to UTC, the hour and minute should be indicated in this sub message. Hour (0-23) should be coded in bits 13 to 9 of the sub message (bit 13 is MSB). Minute (0-59) should be coded in bit 8 to 2 (bit 8 is MSB). Bit 1 and bit 0 are not used.

When slot timeout = 2,4,6 - Then the sub message is the slot number: Slot number used for this transmission (between 0 and 2249).

When slot timeout = 3,5,7 - Then the sub message is the recieved stations: Number of other stations (not own station) which the station currently is receiving (between 0 and 16383).

See Also:

Serialized Form

Field Summary

Fields

Modifier and Type	Field and Description
protected int	slotTimeout SOTDMA Slot Timeout Specifies frames remaining until a new slot is selected 0 means that this was the last transmission in this slot 1-7 means that 1 to 7 frames respectively are left until slot change
protected int	subMessage SOTDMA sub-message This field has many purposes see class description for help:

Fields inherited from class dk.dma.ais.message.AisPositionMessage

cog, navStatus, pos, posAcc, raim, rot, sog, spare, specialManIndicator, syncState, trueHeading, utcSec

Fields inherited from class dk.dma.ais.message.AisMessage

msgId, repeat, userId, VALID_MESSAGE_TYPES, vdm

Constructor Summary

Constructors

Constructor and Description
AisMessage1() Instantiates a new Ais message 1.
AisMessage1(Vdm vdm) Instantiates a new Ais message 1.

Method Summary

Modifier and Type	Method and Description
SixbitEncoder	getEncoded() Abstract method to be implemented by all extending classes
int	getSlotTimeout() Gets slot timeout.
int	getSubMessage() Gets sub message.
void	parse() Parse.
void	setSlotTimeout(int slotTimeout) Sets slot timeout.
void	setSubMessage(int subMessage) Sets sub message.
String	toString()

Methods inherited from class dk.dma.ais.message.AisPositionMessage

encode, getCog, getNavStatus, getPos, getPosAcc, getRaim, getRot, getSensorRot, getSog, getSpare, getSpecialManIndicator, getSyncState, getTrueHeading, getUtcSec, getValidPosition, isCogValid, isHeadingValid, isPositionValid, isRotValid, isSogValid, parse, setCog, setNavStatus, setPos, setPosAcc, setRaim, setRot, setSog, setSpare, setSpecialManIndicator, setSyncState, setTrueHeading, setUtcSec

Methods inherited from class dk.dma.ais.message.AisMessage

getInstance, getMsgId, getRepeat, getSourceTag, getTags, getTargetType, getUserId, getVdm, reassemble, setRepeat, setTag, setTags, setUserId, trimText

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Field Detail

slotTimeout

protected int slotTimeout

SOTDMA Slot Timeout Specifies frames remaining until a new slot is selected 0 means that this was the last transmission in this slot 1-7 means that 1 to 7 frames respectively are left until slot change

subMessage

protected int subMessage

SOTDMA sub-message This field has many purposes see class description for help:

Constructor Detail

AisMessage1

public AisMessage1()

Instantiates a new Ais message 1.

AisMessage1

public AisMessage1(Vdm vdm)
            throws AisMessageException,
                   SixbitException

Instantiates a new Ais message 1.

Parameters:

vdm - the vdm

Throws:

AisMessageException - the ais message exception

SixbitException - the sixbit exception

Method Detail

parse

public void parse()
           throws AisMessageException,
                  SixbitException

Parse.

Throws:

AisMessageException - the ais message exception

SixbitException - the sixbit exception

getEncoded

public SixbitEncoder getEncoded()

Description copied from class: AisMessage

Abstract method to be implemented by all extending classes

Specified by:

getEncoded in class AisMessage

Returns:

SixbitEncoder encoded

getSlotTimeout

public int getSlotTimeout()

Gets slot timeout.

Returns:

the slot timeout

setSlotTimeout

public void setSlotTimeout(int slotTimeout)

Sets slot timeout.

Parameters:

slotTimeout - the slot timeout

getSubMessage

public int getSubMessage()

Gets sub message.

Returns:

the sub message

setSubMessage

public void setSubMessage(int subMessage)

Sets sub message.

Parameters:

subMessage - the sub message

toString

public String toString()

Overrides:

toString in class AisPositionMessage