Refueler
Well-known member
Obviously doesn't ... like most probably a GPS Junkie ! (I do not mean that in any rude way ... its true that many today look at a GPS screen and sail on ... ).
Radar or VHF Assisted Collisions
- Thread starter Stingo
- Start date
Obviously doesn't ... like most probably a GPS Junkie ! (I do not mean that in any rude way ... its true that many today look at a GPS screen and sail on ... ).
Refueler
Well-known member
Think Laika was asking Little Grebe how HE plotted etc. .... as a question based on LG not using his compass.
laika
Well-known member
Yes exactly that! I was actually wondering what the context of Daedelus's post was so you've cleared up the confusion on both our parts
BabySharkDooDooDooDooDoo
Well-known member
I'd suggest that once done a couple of time a sailing trip from (say) Portsmouth to Yarmouth in normal visibility doesn't really need any GPS assistance.
Similarly a trip from the Orwell to Burnham on Crouch is as much about buoy hopping as anything else
Refueler
Well-known member
Fine ... I was hoping that my comment stating I was not trying to be rude was sufficient ...
As a person who sailed Solent on yachts for approx 40years ... I too did not need GPS or even compass to get to any of the havens there ... but I still used them actually .... a) to know when I could get to the pub at the destination .. b) practice !!
Now based in Baltic ... if I cruise - then I do need both as its approx 90nm to Gotland ... then another 90nm to Swedish archipelago
BabySharkDooDooDooDooDoo
Well-known member
No offence taken - get the tide right and the boat will get you almost all the way there to entrance of Lymington or Yarmouth with any help!
Refueler
Well-known member
It also depends which side you run as well ... north along or south along ...
oldmanofthehills
Well-known member
My father an aeronautical engineer explained radar assisted collisions to me about 55 years ago. It is simply the confusion of radar screen image with the outer world. The radar screen shows an object ahead on safe no-collision path so you relax. However the object you should be worrying about is something else. In case of that generation of planes it could be the ground because you are flying too low. For boats it could be a relatively non reflective object ahead of you or something you have got in the way of.
Kukri
Well-known member
Atlantic Empress and Aegean Captain.
Kukri
Well-known member
Classically a radar assisted collision occurs when two vessels are aware of each other on radar but not visually and, owing to faulty plotting or no plotting, they alter course into each other when, had they not altered course, they would have passed clear.
The most notorious radar assisted collision was that between the Stockholm and the Andrea Doria.
This is a very good professional analysis of the incident:
http://www.titanicology.com/AndreaDoria/Stockholm-Andrea_Doria_Collision_Analysis.pdf
The most notorious radar assisted collision was that between the Stockholm and the Andrea Doria.
This is a very good professional analysis of the incident:
http://www.titanicology.com/AndreaDoria/Stockholm-Andrea_Doria_Collision_Analysis.pdf
Refueler
Well-known member
RAC (Radar Assisted Collisions) as it was nicknamed was generally where early operators were confused by RELATIVE and TRUE MOTION on the screens.
Early days screens were relatively small and little actual plotting was done ... with small screens it was common for ship to have a large pad of plotting sheets ...
As time and radar gear moved on ... the screens got larger and it was then possible to use chinagraph pencil and ruler ... often a broken Decca rule ! to plot direct on the glass screen - this went a long way to improve things.
Things were going along well ... RAC events were only matters of conversation after a while ... training was improving and plotting became common place ........................
Then along comes dear old Kelvin Hughes and a radar that was daylight viewable - called Situation Display ... but based only on True Motion ... the radar screen was a small 5" job down in the bowels of the casing ... it then had a TV camera over the top feeding TV based image to a screen for the operator ... about 25" or so .... The targets left a series of dots that joined up into a 'trace' ... the trace stayed for a reasonable time ... before fading out.
I was on a couple of ships that were test-beds for it ... but anyway - it was quite widely sold ...
Its problem was True Track and that 'trace' ... so many operators confused that trace with Relative Motion plot ...
It did not last long before the model was withdrawn and replaced with a more conventionally based design that then led onto the Collision avoidance systems along with many other manufacturers.
Early days screens were relatively small and little actual plotting was done ... with small screens it was common for ship to have a large pad of plotting sheets ...
As time and radar gear moved on ... the screens got larger and it was then possible to use chinagraph pencil and ruler ... often a broken Decca rule ! to plot direct on the glass screen - this went a long way to improve things.
Things were going along well ... RAC events were only matters of conversation after a while ... training was improving and plotting became common place ........................
Then along comes dear old Kelvin Hughes and a radar that was daylight viewable - called Situation Display ... but based only on True Motion ... the radar screen was a small 5" job down in the bowels of the casing ... it then had a TV camera over the top feeding TV based image to a screen for the operator ... about 25" or so .... The targets left a series of dots that joined up into a 'trace' ... the trace stayed for a reasonable time ... before fading out.
I was on a couple of ships that were test-beds for it ... but anyway - it was quite widely sold ...
Its problem was True Track and that 'trace' ... so many operators confused that trace with Relative Motion plot ...
It did not last long before the model was withdrawn and replaced with a more conventionally based design that then led onto the Collision avoidance systems along with many other manufacturers.
PilotWolf
Well-known member
I’d like to think probably wrongly I‘m pretty experienced Not sure how much use I’‘d be with a hand bearing compass.
Radar, EDCIS. Yep!
W
Radar, EDCIS. Yep!
W
awol
Well-known member
I've heard this before - it's mince! If you are moving other than directly towards or away from a land feature its bearing will change, the bearing of a boat on a collision course doesn't.
Refueler
Well-known member
Glad you picked that one up before me ....
The reference for bearing in such a situation HAS to be on the boat you are standing on ... not some distant 3rd party object ...
Even the old suggestion of using a stay or other point on your boat falls apart unless you maintain a steady course .. its why you use a Compass .. so that the heading of you boat makes no difference (deviation accepted of course) ....
BabySharkDooDooDooDooDoo
Well-known member
The moving background trick is, however, useful with some static like a fixed structure or a buoy
awol
Well-known member
Only in that it shows drift when aiming at the buoy.
BabySharkDooDooDooDooDoo
Well-known member
Or when you are aiming elsewhere else but some other force such as the tide has other ideas
capnsensible
Well-known member
It's the other vessel moving relative to the shore. It's easy and effective. Try it.
capnsensible
Well-known member
Unless you haven't got a compass.
Stingo
Well-known member
So far, this thread has been a mine of very useful information. Am pleased I started it and thanks to all who've shared their experience
