Laboratorium RADAR ARPA / GMDSS
A maritime radar with Automatic Radar Plotting Aid (ARPA) capability can create tracks using radar contacts. The system can calculate the tracked object’s course, speed and closest point of approach (CPA), thereby knowing if there is a danger of collision with the other ship or landmass.
A typical ARPA gives a presentation of the current situation and uses computer technology to predict future situations. An ARPA assesses the risk of collision, and enables operator to see proposed maneuvers by own ship.While many different models of ARPAs are available on the market, the following functions are usually provided:
a. True or relative motion radar presentation.
b. Automatic acquisition of targets plus manual acquisition. Digital read-out of acquired targets which provides course, speed, range, bearing, closest point of approach (CPA, and time to CPA (TCPA).
c. The ability to display collision assessment information directly on the PPI, using vectors (true or relative) or a graphical Predicted Area of Danger (PAD) display.
d. The ability to perform trial maneuvers, including course changes, speed changes, and combined course/speed changes. Automatic ground stabilization for navigation purposes.
e. ARPA processes radar information much more rapidly than conventional radar but is still subject to the same limitations.
f. ARPA data is only as accurate as the data that comes from inputs such as the gyro and speed log.
Radio GMDSS Digital Selective Calling (DSC) on MF, HF and VHF maritime radios as part of the GMDSS system. DSC is primarily intended to initiate ship-to-ship, ship-to-shore and shore-to-ship radiotelephone and MF/HF radiotelex calls. DSC calls can also be made to individual stations, groups of stations, or “all stations” in one’s reach. Each DSC-equipped ship, shore station and group is assigned a unique 9-digit Maritime Mobile Service Identity.
DSC distress alerts, which consist of a preformatted distress message, are used to initiate emergency communications with ships and rescue coordination centers. DSC was intended to eliminate the need for persons on a ship’s bridge or on shore to continuously guard radio receivers on voice radio channels, including VHF channel 16 (156.8 MHz) and 2182 kHz now used for distress, safety and calling. A listening watch aboard GMDSS-equipped ships on 2182 kHz