Concept of Collision Point :  The point where two vessel course lines crossed each other.

By the drawing: the speed vector is in 6 minutes interval, there are three collision point (in yellow circle), situation awareness are

• it looks like the vessel on the starboard side has shortest distance of Collision points is more dangerous to Own Ship. (sighted)
• The closer of collision point, the shortest distance has. (sighted)
• The speed vector is in 6 minutes interval which serves to know which targets have potential collision risk  after 6 minutes. (statement)
• Two vessels have collision point did not mean they have collision risk. Collision has another criterion to fulfill to actually happen. (suspect)

Collision happened when two targets arrive same place (collision point) at same time.

If we display the actual ship shape on the drawing, Situation Awareness are

• we can notice immediately that the third vessel is more closer to Own Ship after 6 minutes. (sighted)
• Although fishing vessel 10 on starboard side has the closest collision point No.1, (sighted)
• she arrive the collision point at about 5 minutes later. OS pass No. 1 collision point at about 3 minutes.
• OS and No.10 Fishing Vessel did not arrive No,1 collision point at same time. There will be no collision for OS and NO.10 FV. (statement)
• From this picture, it is hard to say these two vessels on portside which have collision point No.2 and No.3 are arrive at same time with Own ship or not. (suspect)

In here, speed vector is in 3 minutes interval which Situation Awareness are

• No.10 FV is not a threat to OS after three minutes. OS can pass ahead of it. (sighted)
• No.20 Aquarium on port side has arrived collision area(red circle where tow vessel movement are uncertained). (sighted)
• No.30 Mobil on port side is not certained ? (suspect)
• The precaution area is in red circle and ETA to there is 3 Minutes. (statement)

We can make a statement of the speed vector shown ahead of each vessel heading direction.

If the end of two vessel speed vectors close to each other then these two vessels has collision risk. 

在這裡，速度矢量是在3分鐘間隔，情況意識是

No.10 FV在三分鐘後不會對操作系統造成威脅。 操作系統可以超越它。
No.20港口側水族館到達碰撞區（紅圈，拖船運動不確定）
No.30移動端口側不確定
預防區域為紅色圓圈，ETA為3分鐘。
我們可以在每個船隻航向前面顯示速度矢量的聲明。

如果兩個船舶速度向量的結束彼此接近，則這兩個船舶具有碰撞風險。

Let's see  What intention of this No. 20 vessel is?

• Her outbound heading is not straight to the traffic lane in right angle (sighted)
• which means she is more likely to go westbound. (suspect)
• She may go eastbound or unlikely crossing, (suspect)
• We have to wait and see. (sighted)
• Crossing or not, depends on his service route. (statement)
  • Is she a working or supply ship around port area or (suspect)
  • She is an ocean going vessel to join the traffic lane ? (suspect)
  • Often the VTS will make the announcement of outbound vessel. (suspect)
  • or we should keep radio watch of VTS VHF channel. (statement)
• The best choice for Own Ship now is reducing speed to let her pass ahead and fulfill the "safe speed" COLREG. (suspect)
• if target vessel will go eastbound, Own Ship can alter course to starboard to give more sea room for her. (suspect)

• After 45 seconds exercise time (in yellow circle), this vessel "Aquarium" is in collision risk with Own Ship. (sighted)
• and alter course to starboard side can cause another collision risk with fishing boat No. 10. (sighted)
• But "Aquarium" is still inside the harbour limit (sighted)
• Check target vessel position in harbour area can have better understanding of her maneuvering. (statement)
• and she is the give way vessel, we should wait longer although "Aquarium" has only 9 cable away. (suspect)
• or we should further reduce speed (for OS now is making 17.7 knots) (suspect)
• Alter course to starboard side to give more sea room for outbound vessel is not a good choice for NO. 10 vessels on starboard side with closer range. (sighted)

At 01 min 30 seconds Exercise time, situation awareness are

• Starboard side fishing vessel No. 10 is circling around to north and irrelevant now. (sighted)
• "Aquarium" alter course to starboard side. (sighted)
• "Aquarium" is going westbound or go astern of Own Ship ? (suspect)
• Own ship can concentrate on other outbound vessel now which one is probably going eastbound, not likely crossing. (sighted)
• Own ship had reduced the speed to 16.3 Knots now. Originally OS has 19.2 Knots at 90 seconds before. Now we can further reduce the speed or just wait and see.  (suspect)

At 02 min 30 seconds Exercise time, situation awareness are

• Port side Working vessel No. 13 can clear Own Ship bow after three minutes. (sighted)
• "Aquarium" alter course to starboard side go astern of Own Ship. (sighted)
• Port side CTNR vessel No. 18 can clear Own Ship bow after three minutes. (sighted)
• Own ship had reduced the speed to 14.6 Knots now. Originally OS has 19.2 Knots at 02 min 30 seconds before. (sighted)
• Now we can sail with this speed 14.6 knot till all crossing vessel clear OS bow.  (suspect)

At 03 min Exercise time, situation awareness are

• Port side Working vessel No. 13 can clear Own Ship bow after three minutes. (sighted)
• Port side CTNR vessel No. 18 can clear Own Ship bow after three minutes. (sighted)
• The fast No.11 Pilot boat can clear Own Ship bow after three minutes. (sighted)
• Own ship had reduced the speed to 13.9 Knots now. Originally OS has 19.2 Knots at 3 min before. (sighted)
• "Aquarium" alter course to starboard side go astern of Own Ship. (sighted)
• Now we can sail with this speed 13.9 knot till all crossing vessel clear OS bow.  (for sure now)

While everybody happy now, we will further study on this scenario.

• The speed vector involved with collision risk. (statement)
• If we reset Own Ship speed to original 19.2 Knots, the speed vector will show on Radar as above. (sighted)
• Port side Working vessel No. 13 and Port side CTNR vessel No. 18 now have collision risk involved. (sighted)
• we can not sail with this speed 19.2 knot (OS red)to clear Other vessels after three minutes. (sighted)
• What we can sail with this speed 13.9 knot(OS green) till all crossing vessel clear OS bow, for sure. Now all crossing vessels become nightmare to us after three minutes. (sighted)
• More speed, More collision risk. (statement)
• No Speed, No collision risk. (almost) 
• Any uncertainty, stop the engine immediately. (statement)
• While all ship are working against you, just reduce the speed with all means. (statement)  

At 04 min 30 sec Exercise time, situation awareness are

• All Port side vessels will clear Own Ship bow after three minutes. (suspect)
• Own ship had reduced the speed to 12.2 Knots now. Originally OS has 19.2 Knots at beginning. (sighted)
• "Aquarium" alter course to starboard side go westbound. (sighted)
• With the radar speed vector prospect in mind, we can concentrate now
  • on the crossing vessel bearing change (True or relative bearing) till all clear OS bow.  (suspect)
  • on the crossing vessel heading change, if it is an eastbound vessel ? (suspect)
  • if crossing vessel heading change to port side is OK (for sure),
  • if crossing vessel heading change to starboard side will involve new collision risk. (suspect)