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This package supports the parsing of AIS messages in Java. AIS, the Automatic Identification System, is a system aiming at improving maritime safety by exchanging messages between ships, other vehicles in particular aircraft involved in search-and-rescue (SAR), and (fixed) base stations. To be precise, this package support the ITU-R M.1371-4 AIS standard. See our extensive javadoc and in particular the class AISParser for more information on how to use this package. The parser was used in the Poseidon project, and is improved in the Metis project to better handle uncertain information. Both projects were led by the Embedded Systems Institute. In both projects Thales Nederlands was the carrying industrial partner, and multiple Dutch universities participated.
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package nl.esi.metis.aisparser.impl;

import nl.esi.metis.aisparser.AISMessage09;
import nl.esi.metis.aisparser.CommunicationState;
import nl.esi.metis.aisparser.Itdma;
import nl.esi.metis.aisparser.Sixbit;
import nl.esi.metis.aisparser.Sotdma;
import nl.esi.metis.aisparser.UtilsAngle12;
import nl.esi.metis.aisparser.UtilsLatitude27;
import nl.esi.metis.aisparser.UtilsLongitude28;
import nl.esi.metis.aisparser.UtilsPositionInfo;
import nl.esi.metis.aisparser.UtilsSpare;
import nl.esi.metis.aisparser.UtilsTimeStamp;
import nl.esi.metis.aisparser.UtilsTwosComplement;
import nl.esi.metis.aisparser.annotations.AISIllegalValueAnnotation;
import nl.esi.metis.aisparser.provenance.VDMMessageProvenance;

/* ESI AIS Parser
 * 
 * Copyright 2011/2012 by Pierre van de Laar, Pierre America (Embedded Systems Institute)
 * Copyright 2008 by Brian C. Lane 
 * All Rights Reserved
 * 
 */

/** Implementation of AIS Message type 9: Standard SAR Aircraft Position Report.
 *  * Field Nr     Field Name                          NrOf Bits   (from,  to)
 * ------------------------------------------------------------------------
 *  1           messageID                                  6    (   1,   6)
 *  2           repeatIndicator                            2    (   7,   8)
 *  3           userID                                    30    (   9,  38)
 *  4           altitude                                  12    (  39,  50)
 *  5           speedOverGround                           10    (  51,  60)
 *  6           positionAccuracy                           1    (  61,  61)
 *  7           longitude                                 28    (  62,  89)
 *  8           latitude                                  27    (  90, 116)
 *  9           courseOverGround                          12    ( 117, 128)
 * 10           timeStamp                                  6    ( 129, 134)
 * 11           altitudeSensor                             1    ( 135, 135)
 * 12           spare1                                     7    ( 136, 142)
 * 13           dte                                        1    ( 143, 143)
 * 14           spare2                                     3    ( 144, 146)
 * 15           assignedModeFlag                           1    ( 147, 147)
 * 16           raimFlag                                   1    ( 148, 148)
 * 17           communicationStateSelectorFlag             1    ( 149, 149)
 * 18           communicationState                        19    ( 150, 168)
 *                                                      ---- +
 *                           (maximum) number of bits    168
 * 
 * @author Pierre van de Laar
 * @author Pierre America
 * @author Brian C. Lane
 */
class AISMessage09Impl extends AISMessageImpl implements AISMessage09 {
	public static final int LENGTH = 168;

	public static boolean validLength(int length)
	{
		return (length == LENGTH);
	}

	/**
	 * Return the difference in available and needed bits to parse this sixbit as an AISMessage
	 * A positive difference indicates that there are more bits available than needed by the standard.
	 * @param sb
	 * @return
	 */
	public static int differenceInBits(Sixbit sb)
	{
		return (sb.available() - LENGTH);
	}

	private static final int ALTITUDE_FROM = 39;
	private static final int ALTITUDE_TO = 50;

	private int altitude;
	/** altitude
	 * @return int value of altitude (12 bits [39,50])
	 */
	public int getAltitude() { return altitude; }


	private static final int SPEEDOVERGROUND_FROM = 51;
	private static final int SPEEDOVERGROUND_TO = 60;

	private int speedOverGround;
	/** speedOverGround
	 * @return int value of speedOverGround (10 bits [51,60])
	 */
	public int getSpeedOverGround() { return speedOverGround; }


	private static final int POSITIONACCURACY_BITINDEX = 61;

	private boolean positionAccuracy;
	/** positionAccuracy
	 * @return boolean value of positionAccuracy (bit 61)
	 */
	public boolean getPositionAccuracy() { return positionAccuracy; }


	private static final int LONGITUDE_FROM = 62;
	private static final int LONGITUDE_TO = 89;

	private double longitude;
	/** longitude
	 * @return double value of longitude (28 bits [62,89])
	 */
	public double getLongitudeInDegrees() { return longitude; }


	private static final int LATITUDE_FROM = 90;
	private static final int LATITUDE_TO = 116;

	private double latitude;
	/** latitude
	 * @return double value of latitude (27 bits [90,116])
	 */
	public double getLatitudeInDegrees() { return latitude; }


	private static final int COURSEOVERGROUND_FROM = 117;
	private static final int COURSEOVERGROUND_TO = 128;

	private int courseOverGround;
	/** courseOverGround
	 * @return int value of courseOverGround (12 bits [117,128])
	 */
	public int getCourseOverGround() { return courseOverGround; }


	private static final int TIMESTAMP_FROM = 129;
	private static final int TIMESTAMP_TO = 134;

	private int timeStamp;
	/** timeStamp
	 * @return int value of timeStamp (6 bits [129,134])
	 */
	public int getTimeStamp() { return timeStamp; }


	private static final int ALTITUDESENSOR_BITINDEX = 135;

	private boolean altitudeSensor;
	/** altitudeSensor
	 * @return boolean value of altitudeSensor (bit 135)
	 */
	public boolean getAltitudeSensor() { return altitudeSensor; }


	private static final int SPARE1_FROM = 136;
	private static final int SPARE1_TO = 142;

	private int spare1;
	/** spare1
	 * @return int value of spare1 (7 bits [136,142])
	 */
	public int getSpare1() { return spare1; }


	private static final int DTE_BITINDEX = 143;

	private boolean dte;
	/** dte
	 * @return boolean value of dte (bit 143)
	 */
	public boolean getDte() { return dte; }


	private static final int SPARE2_FROM = 144;
	private static final int SPARE2_TO = 146;

	private int spare2;
	/** spare2
	 * @return int value of spare2 (3 bits [144,146])
	 */
	public int getSpare2() { return spare2; }


	private static final int ASSIGNEDMODEFLAG_BITINDEX = 147;

	private boolean assignedModeFlag;

	/** Returns the assigned mode flag.
	 * @return a boolean value representing the assigned mode flag: 

	 * false = Station operating in autonomous and continuous mode 

	 * true = Station operating in assigned mode
	 */
	public boolean getAssignedModeFlag() { return assignedModeFlag; }


	private static final int RAIMFLAG_BITINDEX = 148;

	private boolean raimFlag;
	/** raimFlag
	 * @return boolean value of raimFlag (bit 148)
	 */
	public boolean getRaimFlag() { return raimFlag; }


	private static final int COMMUNICATIONSTATESELECTORFLAG_BITINDEX = 149;

	private boolean communicationStateSelectorFlag;
	/** communicationStateSelectorFlag
	 * @return boolean value of communicationStateSelectorFlag (bit 149)
	 */
	public boolean getCommunicationStateSelectorFlag() { return communicationStateSelectorFlag; }


	private static final int COMMUNICATIONSTATE_FROM = 150;
	//private static final int COMMUNICATIONSTATE_TO = 168;

	private CommunicationState communicationState;
	/** communicationState
	 * @return CommunicationState value of communicationState (19 bits [150,168])
	 */
	public CommunicationState getCommunicationState() { return communicationState; }


	/** AISMessage 9 constructor
	 * @param content AIS content
	 * @param prov the provenance of the message
	 * @precondition validLength(content.length()) && AISMessageBase.getMessageId(content)==9
	 */
	public AISMessage09Impl(Sixbit content, VDMMessageProvenance prov)
	{
		super(content, prov);
		assert(validLength(content.length()));
		assert(getMessageID() == 9);

		altitude = content.getIntFromTo(ALTITUDE_FROM,ALTITUDE_TO);
		speedOverGround = content.getIntFromTo(SPEEDOVERGROUND_FROM,SPEEDOVERGROUND_TO);
		positionAccuracy = content.getBoolean(POSITIONACCURACY_BITINDEX);
		longitude = UtilsLongitude28.toDegrees( UtilsTwosComplement.convertFrom28Bits( content.getIntFromTo(LONGITUDE_FROM,LONGITUDE_TO) ) );
		if (!UtilsPositionInfo.isLongitudeSemanticallyCorrect(longitude))
		{
			annotations.add (new AISIllegalValueAnnotation("getLongitudeInDegrees", longitude, UtilsPositionInfo.rangeLongitude));
		}
		latitude = UtilsLatitude27.toDegrees( UtilsTwosComplement.convertFrom27Bits( content.getIntFromTo(LATITUDE_FROM,LATITUDE_TO) ) );
		if (!UtilsPositionInfo.isLatitudeSemanticallyCorrect(latitude))
		{
			annotations.add (new AISIllegalValueAnnotation("getLatitudeInDegrees", latitude, UtilsPositionInfo.rangeLatitude));
		}
		courseOverGround = content.getIntFromTo(COURSEOVERGROUND_FROM,COURSEOVERGROUND_TO);
		timeStamp = content.getIntFromTo(TIMESTAMP_FROM,TIMESTAMP_TO);
		altitudeSensor = content.getBoolean(ALTITUDESENSOR_BITINDEX);
		spare1 = content.getIntFromTo(SPARE1_FROM,SPARE1_TO);
		if (!UtilsSpare.isSpareSemanticallyCorrect(spare1))
		{
			annotations.add(new AISIllegalValueAnnotation("getSpare1", spare1, UtilsSpare.range));
		}
		dte = content.getBoolean(DTE_BITINDEX);
		spare2 = content.getIntFromTo(SPARE2_FROM,SPARE2_TO);
		if (!UtilsSpare.isSpareSemanticallyCorrect(spare2))
		{
			annotations.add(new AISIllegalValueAnnotation("getSpare2", spare2, UtilsSpare.range));
		}
		assignedModeFlag = content.getBoolean(ASSIGNEDMODEFLAG_BITINDEX);
		raimFlag = content.getBoolean(RAIMFLAG_BITINDEX);
		communicationStateSelectorFlag = content.getBoolean(COMMUNICATIONSTATESELECTORFLAG_BITINDEX);
		if (communicationStateSelectorFlag)
		{
			communicationState = new Itdma(COMMUNICATIONSTATE_FROM, content);
		}
		else
		{
			communicationState = new Sotdma(COMMUNICATIONSTATE_FROM, content);
		}	    	
	}
	
	
	/** Returns the speed over ground as a string.
	 * @return a string representing the speed over ground
	 */
	public String getAltitudeString() {
		String altString;
		if (altitude == 4095)
			altString = "not available";
		else if (altitude == 4094)
			altString = ">=4094";
		else
			altString = Integer.toString(altitude);
		return altString;
	}
	
	/** Returns the speed over ground as a string.
	 * @return a string representing the speed over ground
	 */
	public String getSpeedOverGroundString() {
		String sogString;
		if (speedOverGround == 1023)
			sogString = "no SOG";
		else if (speedOverGround == 1022)
			sogString = ">=1022";
		else
			sogString = Integer.toString(speedOverGround);
		return sogString;
	}
	
	/** Generates a String representing the AIS message. 
	 * Format: all fields are shown in the order as specified by the standard separated by the SEPARATOR string.
	 */
	@Override
	public String toString() {
		String result = super.toString();
		result += SEPARATOR + getAltitudeString();
		result += SEPARATOR + getSpeedOverGroundString();
		result += SEPARATOR + (positionAccuracy ? "high" : "low") + " accuracy";
		result += SEPARATOR + UtilsPositionInfo.longitudeToString(longitude);
		result += SEPARATOR + UtilsPositionInfo.latitudeToString(latitude);
		result += SEPARATOR + UtilsAngle12.toString(courseOverGround);
		result += SEPARATOR + UtilsTimeStamp.toString(timeStamp);
		result += SEPARATOR + (altitudeSensor ? "barometic" : "GNSS");
		result += SEPARATOR + (dte ? "no DTE" : "with DTE");
		result += SEPARATOR + (assignedModeFlag ? "assigned" : "autonomous") + " mode";
		result += SEPARATOR + "RAIM " + (raimFlag ? "in use" : "not in use");
		result += SEPARATOR + (communicationStateSelectorFlag ? "ITDMA" : "SOTDMA");
		result += SEPARATOR + communicationState.toString();
		return result;		
	}
}