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Author Topic: ARPA  (Read 11737 times)

January 12, 2016, 06:08:02 PM
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CAN someone PLEASE  :'(explain how to use ARPA ? what's the function of arpa logg ? when i'm tracking, and can see the other vessels relativ vektor on the radar, i still cant get his relativ speed , course and etc...why ? how to use the trail maneuver ?

January 13, 2016, 11:26:42 AM
Reply #1
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Hello deo!

Arpa interface:
ARPA: Contact 1 (selected contact to track)
CPA:  (closest point of approach)
TCPA: (time of the closest point of approach)
Range:  (distance to target/contact in Nm or "c", Cable lenght = 185.2 m)
Bearing: (bearing -azimuth- of contact relative to your vessel)
Relative co: (contact´s course relative to your ship/observed from your ship)
Relative sp: (contact´s speed  relative to your ship)
True co: (true/exact course of contact)
true sp: (true/exact speed of contact)

ARPA Log: function of arpa log is intended for manual input of contact position so that radar system can  calculate solution of target(contact) speed, course, CPA etc...
Let´s say that you see on your radar PPI (Plan Position Indicator/Display) a contact which is not automatically detected by ARPA and you want to determine his speed, course and other parameters.
Select on ARPA contact to have "M" designation, lets say M1 (M = manual )
You scroll radar cursor with arrow buttons over contact and press "log" button.
Contact current position,range and bearing is logged.
After few minutes you press "log" button again and now system have necessary data to calculate target speed,course and other information. It is basic calculation of two selected points in space to calculate object´s distance traveled and course in given time.
Now your radar system have enough information to calculate all necessary parameters to display contact CPA, TCPA, course, speed etc.

ARPA Trial: it simulates your ship alternative course and speed.
With trial maneuver on radar display you can test and decide what shall be your next  move/maneuver in relation to other contact. ARPA Log (manual target tracking) is very well suited for that because automatic target tracking constantly resets contact on original position after few sweeps of radar antenna. While arpa Log (contact M1,M2,...so on) do not resets and require your manual input for next calculation.
« Last Edit: January 13, 2016, 01:13:46 PM by yamato980 »

January 13, 2016, 08:44:35 PM
Reply #2
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OK! ;Dcan you explain step by step how to trail maneuver?when i go in trail mode and change speed and course. it seems like it the targets speed and course that changes...  Thanks for the help  :)
« Last Edit: January 13, 2016, 08:55:48 PM by deo »

January 14, 2016, 02:21:27 PM
Reply #3
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Yes,the system applies new (hypothetical) course and speed of your ship and then "shifts"and moves other targets around your ship to represent possible future positions of radar targets if user decide to go with this maneuver (course and speed).

I seldom use this option but it can be of help if you have enough time to examine possible future moves.
Here is how you can use it.

Select in "arpa vector" mode "relative" presentation of contac movement
Set in "arpa vector" mode to some longer time,say 10-15min.
Enable trial mode and set desired course and speed.
Now turn back to "arpa vector" and increase time until all vector length´s become relatively long.
So that you have visual info where other targets move in relation to your new course and speed.
Arpa will trigger alarm if some targets "fit in" arpa alarm parameters.
You can now experiment with course and speed of your ship, and time in "arpa vector" to see and select your best move.
also you can scroll trough all contacts in "arpa" mode to see their data in trial mode, rel speed, rel course etc...

January 17, 2016, 07:52:47 PM
Reply #4
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does it(arpa) have a time delay function ? which make it possible see the outcome of a maneuver depending on time one choose to change course for example ?

January 18, 2016, 02:38:52 PM
Reply #5
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This program dont have such ability.

March 26, 2020, 04:33:16 PM
Reply #6
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just to point out, real radars do have a time delay which you can set and rates of turn etc as they are often very significant in confined waters