Partially correct , if relative vector of the target is chosen the aspect of the vessel will not change irrespective of ground stabilisation or sea stabilisation. This problem occurs only when using the true vector.
(b) Proper use shall be made of radar equipment if fitted and operational, including long-range scanning to obtain early warning of risk of collision and radar plotting or equivalent systematic observations of detected objects. (c) Assumptions shall not be made on the basis of scanty information, especially scanty radar information.
The question is still there. What if you have restricted visibility? Why is it so important to have input speed through the water (using mechanical log, or dopler at big depth which might be unreliable) instead of using SOG (GPS) and just change from true to relative vectors? And in any situation one or both vessels must alter the course to starboard so i can't see any confusion here.
Whether it is RV or clear visibility, interpretation of Arpa details w.r.t cpa determination remains same. Action to be taken for crossing as well as head-on remains same however interpretation of situation whether it is head-on or crossing will be determined using STW and not SOG. In clear weather with no current, if you are using true vectors and true trails than for a crossing situation the trails will appear to be at crossing angles and if their is a current in a head on situation and you have true trails than also the trails will be at crossing angles (it will appear as a crossing situation) which is not true as head on situation is determined by a vsls heading and not COG. This is the only importance for using STW. Every equipment has error whether it is Speed log or GPS or even ARPA but so far as they meet the performance standards they all are accepted for use. I hope you get my point ☺️
In short, its simply about aspect clarity.. however the down side is ships are affected differenty by wind and current, so in water stabilized IF you were using TRUE vectors to asses risk of collision, you might get false answers.
I used sog on radar, who cares? Ground stabilized relative trail with range ring on. No need to aquire target, 1 look at radar i know cpa and tcp right away, no need to wait couple of minutes to have accurate figures. Only disadvantage it dont trigger cpa warning alarm.
For aspect - Imagine you are on Vsl A and target vsl is B, now imagine yourself in vsl B. The ANGLE between vsl B heading and bearing of vsl A from vsl B is called as aspect. Now come back to your vsl A...Now whichever light you see of target vsl B is how you decide whether it's color red or color green.
Yup will tell you in short but it will b worth - 1. Before starting radar make sure u inspect scanner is clear of everything. 2. It has gain - it is basically adjusting receiving antenna sensitivity. Sea clutter knob- to adjust clutter caused around ship due to wind. Sea clutter should not be completely eliminated as it will eliminate small targets too. Rain clutter - used to penetrate rain drops and paint a target, it can also b used to eliminate clouds. 3. Best radar setup is true trails and relative vector as u can see past posn of ship by its trails and whether it will approach u or not will b determined by relative vector. 4. Relative motion or true motion depends on individual to individual. 5. When transiting near land / coastal - keep on ground stabilization to determine course over ground And for collision avoidance use sea stabilization that is STW. I hope this would help you.
Collision avoidance is always with respect to heading thus as per recommendation for old radars u have error of 7 cables and for new radar error is till 3cable
@@SailorVikas Collision Avoidance is a too generic term, which does not reveal whether radar is being used for finding out of target, or , for knowing how close the target will pass, or, for deciding what is the best action for avoiding collision. Also, 'the recommendation". , what is the source of this information?
@@alaguvel5850 if possible have the tendency to use the word could, please, as he is helping and you are commanding him.... Konjam mariyatha pesunga comment pannunga..
Bro one question, in jrc JQX-30A model SART have two option "ON" &"OFF".No "TEST" Option then how I will test as I didn't get anything in manual about test procedure
What about if the target vessel has strong sidewind, her True Course is let's say 090 deg, but the bow pointed to 045deg, so what you see on radar wont correspond to what you observe visually. Or the influence of wind isnt important in the case of radar plotting? Pls explain
@@SailorVikas with respect, so my question isnt dumb as i suppose? i mean we just assume that conditions are the same because we are close, but theoretically situation i described could take place? Radar detects by consecutive bearings only the true course path of the vessel but he cant know the heading(of course if the info from AIS isnt supplied)
Fundamentally disagree. Both SOG and STW are fine for collision avoidance. Determining aspect based on RADAR observations is a BAD and DANGEROUS practice. Remember that crossing rules apply only to vessels "in sight of one another" therefore if you want to know you aspect, look out of the window, not your at your RADAR
Hello ....thanks for commenting....determine aspect is based on calculation in radar plotting.... visually seeing u cannot calculate his heading....u have to use available tools to measure degrees of red or green aspect ...I hope u understand !
@@SailorVikas you don't need to "calculate his heading" in order to apply to apply RoR or for collision avoidance. During daytime you will clearly see if you can see his port or stbd side just by visual observation at night it is even easier since you will see his lights, this is all you need to know to apply rules properly. STW has many inherent innaccuarcies that make it unreliable. Use your eyes to determine aspect and apply the rules.
@@Wolfy8668 noted urs and I understand yours ...but exam point of view ...when it is asked to determine aspect....u have to calulate that aspect in degrees.....which u cannot determine by simple seeing the other target visually....u have to have other ships hdg to determine aspect in degrees .....this is taught in radar / arpa course after 2nd mates and it's also their in radar arpa book of Subramanium....I hope you get what I am trying to convey.
@@SailorVikas i understand that examiners are sometimes hard headed but then again they are only human and can be wrong. In this case practice is more important, we already have to many "armchair" navigators out there. The fact of the matter is that on modern systems ground stabilisation is perfectly acceptable for collision avoidance "provided that the OOW understand benefits and limitations of such set up"
@@Wolfy8668 yes whatever you saying is practically correct but when it comes to orals....you have to say what is surveyor expecting from u....that is stw to be used for collision avoidance...and never speed over ground...speed over ground only to be used during arrival departure ports. If you use speed over ground for collision avoidance and if their is easterly current...the vector will appear in radar as crossing in true motion and this creates confusion for the OOW...about whether it is crossing or head on....that's the reason when u use speed thru water in easterly current....u will get proper vectors in radar which eliminates the confusion as head-on situation is considered when hdgs are reciprocal and not the course over ground being reciprocal.
