Furuno FEA-2807 - 21 AIS Target Functions; Introduction

21-1
21. AIS Target Functions
21.1 Introduction
An AIS transponder can be connected to the ECDIS to display AIS targets received from an AIS transponder. The
ECDIS can store up to 1,500 AIS targets in its storage buffer. When this buffer becomes full of AIS targets, the alert
639 is generated to alert you that the storage buffer is full. The storage buffer contains automatic dead reckoning for
all AIS targets, which is based on reported Speed Over Ground (SOG), Course Over Ground (COG), Rate Of Turn
(ROT) and heading. The storage buffer also contains calculation of range, bearing, CPA, TCPA, etc. The CPA and
TCPA limits set for dangerous targets are common for TT and AIS targets.
ECDIS can display AIS targets that are within the operator-defined range (max. range is 48 nm). The maximum
number of targets that can be displayed is 240 and the operator may select the number of targets to display. For
details, see section 21.3 "How to Display AIS Targets".
The frequency for update of AIS transponder-sent data depends on speed and course of tracked AIS target. The table
below shows the IMO standardized reporting rates for the AIS transponder. Based on the table below, the ECDIS
defines which AIS targets are in tracking or lost. When you acknowledge the lost target alert, the AIS symbol is
removed from the ECDIS display. If a lost target is not acknowledged, the AIS symbol is automatically removed as
shown in table below.
Type of Ship
IMO
nominal
reporting
interval
Lost target
indication
(reporting
interval >)
Pre-set rate
for automatic
removal of
lost target
Class A: speed between 0-14 kn 10 s 50 s 430 s
Class A: speed between 14 - 23 kn 6 s 30 s 430 s
Class A: speed greater than 23 kn 2 s 10 s 430 s
Class A: anchored, moored, not under control or grounded, speed
between 0-3 kn
3 min 10 min 36 min
Class A: anchored, moored, not under control or grounded, speed
greater than 3 kn
10 s 50 s 36 min
Class B: CS speed between 0 – 2 kn 3 min 10 min 36 min
Class B: CS speed greater than 2 kn 30 s 150 s 430 s
Class B: SOTDMA speed between 0 – 2 kn 3 min 10 min 36 min
Class B: SOTDMA speed between 2 - 14 kn 30 s 150 s 430 s
Class B: SOTDMA speed between 14 - 23 kn 15 s 75 s 430 s
Class B: SOTDMA speed greater than 23 kn 5 s 25 s 430 s
Class A and Class B: no speed available N/A 10 min 36 min
ATON 3 min 10 min 30 min
SAR 10 s 50 s 430 s
Base station 10 s 50 s 430 s
SART N/A 10 min 30 min
An AIS transponder "sees" all ships fitted with an AIS transponder belonging to either
• Class A AIS
• Class B AIS