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1.1 FUNCTIONS
This equipment is a high-performance radar equipment consisting of a scanner unit, a transmitter-
receiver unit and a 29-inch color raster-scan CRT display unit.
This radar complies with the current performance standards of the IMO.
1.1.1 Functions of This System
The JMA-9800 ARPA series is a color radar system designed to comply with the international standards
of the IMO. The main functions include; sea clutter and rain/snow clutter suppression, sensitivity
adjustment, interference reflector, bearing and range measurement using a trackball, fixed/variable range
markers, and electronic bearing line, and ARPA functions (automatic/manual target acquisition and
tracking, vector and trail displays, alarm displays and trial maneuvering).
In addition, the equipment has the functions of color display setting (4 views), own track display, NAV
line and marker displays, TM (True Motion) presentation, Self-diagnostic facilities, and radar
performance monitoring (Performance Monitor). As an option, the radar of 3-units switchover function
(Interswitch) is also available.
1.1.2 ARPA Functions
The ARPA functions that the JMA-9800 series incorporates will be outlined below.
[
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] First Stage: Target Detection from Radar Information
This work corresponds to plotting targets by hand on the radar display. Assume that a ship is
approaching the own ship. You can catch the ship on the radar. Signals from the ship are processed with
the data processor and are transferred to the computer as signals of bearing and range related to the own
ship. In this stage, the system has the functions to quantize radar information, to reject noises, to
eliminate any information other than ship information and to transfer necessary position data of ships to
the computer.
[
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] Second Stage: Target Tracking
Targets are plotted at intervals of 3 to 6 minutes with the radar, but tracking on this system is to plot
them electrically at intervals of fixed times. This means to compare target position data to be detected
every moment with those detected previously so as to check if they are of the same target and also to
save data of the target in its file so as to calculate changes of position data of the target.
[
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] Third Stage: Judgment of Existence of Ship in Danger of Collision
In this stage, the system calculates speeds and courses of a target ship from ever-changing position data
of the target ship obtained in the previous stage so as to judge existence of any danger of collision.
After the calculation, the system can easily calculate the Closest Point of Approach (CPA) to the own
ship and the time required to reach the CPA (TCPA = Time to CPA). Both the CPA and the TCPA are
compared with the preset values previously set according to the situations of the own ship so as to judge
existence of any danger of collision.
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