In what case AIS Message Type 3 should be transmitted?

[Wittgenstein]

Hi, I am a new comer. Having read the discussion on the topic of "Shipping Containers on Radar," I come to join here to get your helps.

My recent interest is focused on 27 types of AIS messages, esepecially on AIS message type 3.

The usage of AIS Message Type 3, which I found through surfing the Internet, is as follows :

(1) "AIS Message 3 is a special or interrogation position report that is commanded*using AIS message 15"

(2) "Message 3 transmission is ITDMA based and is used*when a ship is announcing a need for extra slots due to increased reporting rate,*
usually related to a change in speed or cruising direction."*


Here, my puzzle is "Is the above (1) and (2) just the same case, or two separate cases?"

I need a clear answer from you, AIS users.

The below raw data of AIS Message Type 3 is of the sunken Ferry Sewol on April 16 2014.

$IEC01,VTS1004,4403318,P,0,20140416084837|!AIVDM,1 ,1,,B,16SWOT002ga0VwpCS9L5B4Fv2D9:,0*0B^65
$IEC03,VTS1004,4403310,P,0,20140416084913|!AIVDM,1 ,1,,B,36SWOT0Ojc90Wj@CS3i5eDdJ20sQ,0*6D^0E
$IEC03,VTS1004,4403310,P,0,20140416084919|!AIVDM,1 ,1,,B,36SWOT0Oja90WojCS2kmm4nV20wh,0*48^5F
$IEC03,VTS1004,4403310,P,0,20140416084919|!AIVDM,1 ,1,,A,36SWOT0Oja90WojCS2kmm4nV21Ri,0*6E^06
$IEC03,VTS1004,4403318,P,0,20140416084919|!AIVDM,1 ,1,,B,36SWOT0Oja90WojCS2kmm4nV20wh,0*48^57
$IEC03,VTS1004,4403318,P,0,20140416084919|!AIVDM,1 ,1,,A,36SWOT0Oja90WojCS2kmm4nV21Ri,0*6E^0E
$IEC03,VTS1004,4403310,P,0,20140416084925|!AIVDM,1 ,1,,B,36SWOT0OjW90WtdCS1mEv52j2271,0*27^36
$IEC03,VTS1004,4403310,P,0,20140416084926|!AIVDM,1 ,1,,B,36SWOT0OjW90WuJCS1c60E4l2000,0*47^53
$IEC03,VTS1004,4403310,P,0,20140416084930|!AIVDM,1 ,1,,A,36SWOT0OjU90WwtCS10n=m<t20q0,0*05^10
$IEC03,VTS1004,4403310,P,0,20140416084931|!AIVDM,1 ,1,,A,36SWOT0OjU90WwtCS10n=m>j22h1,0*03^11
$IEC03,VTS1004,4403308,P,0,20140416084936|!AIVDM,1 ,1,,A,36SWOT0OjP90`1vCRww6`UU82000,0*2A^46
$IEC03,VTS1004,4403310,P,0,20140416084937|!AIVDM,1 ,1,,B,36SWOT0OjN90`26CRwlFdma:23@A,0*17^06
$IEC03,VTS1004,4403310,P,0,20140416084956|!AIVDM,1 ,1,,A,36SWOT0Oj?a0Ww`CRumWaW;P2000,0*06^10
$IEC03,VTS1004,4403318,P,0,20140416084956|!AIVDM,1 ,1,,A,36SWOT0Oj?a0Ww`CRumWaW;P2000,0*06^18
$IEC03,VTS1004,4403318,P,0,20140416085016|!AIVDM,1 ,1,,A,36SWOT0Oica0We<CRspaQGnB2000,0*5D^38
$IEC03,VTS1004,4403318,P,0,20140416085019|!AIVDM,1 ,1,,A,36SWOT0Oica0WcDCRsi9bWtJ21OQ,0*4C^20
$IEC03,VTS1004,4403318,P,0,20140416085020|!AIVDM,1 ,1,,B,36SWOT0Oica0WcDCRsi9bWtJ210P,0*31^22
$IEC03,VTS1004,4403310,P,0,20140416085025|!AIVDM,1 ,1,,B,36SWOT0Oica0WWTCRsaaiH4T227Q,0*0A^67
$IEC03,VTS1004,4403318,P,0,20140416085025|!AIVDM,1 ,1,,B,36SWOT0Oica0WWTCRsaaiH4T227Q,0*0A^6F
$IEC03,VTS1004,4403318,P,0,20140416085026|!AIVDM,1 ,1,,B,36SWOT0Oiba0WTLCRsTasp4T2000,0*63^71
$IEC03,VTS1004,4403318,P,0,20140416085031|!AIVDM,1 ,1,,A,36SWOT0Oiaa0WNPCRsOb<p<f22lQ,0*37^22
$IEC03,VTS1004,4403318,P,0,20140416085037|!AIVDM,1 ,1,,B,36SWOT0Oi`a0WHTCRsM:IH>r23Ai,0*22^35
$IEC03,VTS1004,4403310,P,0,20140416085037|!AIVDM,1 ,1,,B,36SWOT0Oi`a0WHTCRsM:IH>r23Ai,0*22^3D
$IEC03,VTS1004,4403310,P,0,20140416085046|!AIVDM,1 ,1,,B,36SWOT0Oi`a0W>pCRsObdpC<2000,0*27^3B
$IEC03,VTS1004,4403310,P,0,20140416085050|!AIVDM,1 ,1,,A,36SWOT0Oiaa0W<dCRsObg8E@20v@,0*34^2D
$IEC03,VTS1004,4403318,P,0,20140416085050|!AIVDM,1 ,1,,A,36SWOT0Oiaa0W<dCRsObg8E@20v@,0*34^25
$IEC03,VTS1004,4403318,P,0,20140416085056|!AIVDM,1 ,1,,A,36SWOT0Oiba0W30CRsd;2pMR2000,0*2F^4B
$IEC03,VTS1004,4403310,P,0,20140416085057|!AIVDM,1 ,1,,A,36SWOT0Oiba0W30CRsd;2pMR2000,0*2F^42
$IEC03,VTS1004,4403310,P,0,20140416085100|!AIVDM,1 ,1,,B,36SWOT0Oiba0W18CRsi;6`QV20uh,0*3A^52
$IEC03,VTS1004,4403318,P,0,20140416085100|!AIVDM,1 ,1,,B,36SWOT0Oiba0W18CRsi;6`QV20uh,0*3A^5A
$IEC03,VTS1004,4403318,P,0,20140416085109|!AIVDM,1 ,1,,A,36SWOT0PAWa0VmTCRt<cRGj42110,0*07^1B
$IEC03,VTS1004,4403310,P,0,20140416085109|!AIVDM,1 ,1,,A,36SWOT0PAWa0VmTCRt<cRGj42110,0*07^13
$IEC03,VTS1004,4403318,P,0,20140416085113|!AIVDM,1 ,1,,B,36SWOT0PAVa0Vl`CRtAcUWh620vA,0*6D^0F
$IEC03,VTS1004,4403310,P,0,20140416085116|!AIVDM,1 ,1,,A,36SWOT0PATa0VilCRtKcgof<2000,0*56^48
$IEC03,VTS1004,4403318,P,0,20140416085116|!AIVDM,1 ,1,,A,36SWOT0PATa0VilCRtKcgof<2000,0*56^40
$IEC03,VTS1004,4403310,P,0,20140416085125|!AIVDM,1 ,1,,B,36SWOT0PALa0VbDCRtvd8GdN22:Q,0*3A^55
$IEC03,VTS1004,4403318,P,0,20140416085125|!AIVDM,1 ,1,,B,36SWOT0PALa0VbDCRtvd8GdN22:Q,0*3A^5D
$IEC03,VTS1004,4403310,P,0,20140416085130|!AIVDM,1 ,1,,A,36SWOT0PAGa0VUtCRuJ<FGbb20uh,0*70^6E
$IEC03,VTS1004,4403318,P,0,20140416085130|!AIVDM,1 ,1,,A,36SWOT0PAGa0VUtCRuJ<FGbb20uh,0*70^66
$IEC03,VTS1004,4403310,P,0,20140416085131|!AIVDM,1 ,1,,A,36SWOT0PAGa0VUtCRuJ<FGbb22hA,0*46^5C
$IEC03,VTS1004,4403310,P,0,20140416085136|!AIVDM,1 ,1,,A,36SWOT0PABa0VRlCRuk<S7bn2000,0*3F^55
$IEC03,VTS1004,4403310,P,0,20140416085137|!AIVDM,1 ,1,,B,36SWOT0PAAa0VQpCRuu<`obr23AQ,0*5A^30
$IEC03,VTS1004,4403318,P,0,20140416085137|!AIVDM,1 ,1,,B,36SWOT0PAAa0VQpCRuu<`obr23AQ,0*5A^38
$IEC03,VTS1004,4403310,P,0,20140416085144|!AIVDM,1 ,1,,A,36SWOT001<a0VNhCRvK<moc623mA,0*7A^16
$IEC03,VTS1004,4403310,P,0,20140416085146|!AIVDM,1 ,1,,B,36SWOT001<a0VNhCRvK<moc>2000,0*5E^36
$IEC03,VTS1004,4403318,P,0,20140416085146|!AIVDM,1 ,1,,B,36SWOT001<a0VNhCRvK<moc>2000,0*5E^3E
$IEC03,VTS1004,4403318,P,0,20140416085149|!AIVDM,1 ,1,,A,36SWOT0019a0VMPCRvb<rocB2120,0*2A^46
$IEC03,VTS1004,4403318,P,0,20140416085156|!AIVDM,1 ,1,,A,36SWOT0015a0VKDCRw8=5WcJ2000,0*1A^7B
$IEC03,VTS1004,4403310,P,0,20140416085156|!AIVDM,1 ,1,,A,36SWOT0015a0VKDCRw8=5WcJ2000,0*1A^73
$IEC03,VTS1004,4403310,P,0,20140416085200|!AIVDM,1 ,1,,B,36SWOT0011a0VIhCRwNe=ocV212h,0*6A^04
$IEC03,VTS1004,4403318,P,0,20140416085206|!AIVDM,1 ,1,,B,36SWOT000va0VHlCRwh=C7cl2000,0*10^06
$IEC03,VTS1004,4403310,P,0,20140416085207|!AIVDM,1 ,1,,B,36SWOT000va0VHlCRwh=C7cl2000,0*10^0F
$IEC03,VTS1004,4403318,P,0,20140416085210|!AIVDM,1 ,1,,A,36SWOT000sa0VGTCS0;eI7b220v0,0*7F^1E
$IEC03,VTS1004,4403310,P,0,20140416085210|!AIVDM,1 ,1,,A,36SWOT000sa0VGTCS0;eI7b220v0,0*7F^16
$IEC01,VTS1004,4403318,P,0,20140416085213|!AIVDM,1 ,1,,B,16SWOT000ra0VG@CS0@eKGb626s@,0*15^00
$IEC01,VTS1004,4403310,P,0,20140416085213|!AIVDM,1 ,1,,B,16SWOT000ra0VG@CS0@eKGb626s@,0*15^08
$IEC03,VTS1004,4403318,P,0,20140416085216|!AIVDM,1 ,1,,A,36SWOT000qa0VFtCS0M=OWb<2000,0*5C^3C

[Celestialsailor]

This would be your best choice to find answers to your question.
http://www.cruisersforum.com/forums/f13/
Welcome to the forum.