course relative to bearing help ?

[flag4]

hi hunters

could someone please explain 'course relative to bearing' :damn:

if a ship is spotted at 301 degrees, what is the bearing relative to me ?

im watching olc's tutorial and trying to understand the bit where he is plotting the course of the ship, and, he says its 59 degrees relative to his course.

ive treid to work this out on my own and it doesnt add up, coz i know something happens when a ship is moving away from, like, subtracting the 301 from 360 which gives 59. and yet this doent always seem to work.

ive tried it with numerous different courses and i can not get the maths to work - and i have to say its driving me nuts: is there a formula for this ?

ie; when a ship is coming to me and when a ship is moving away.
im very confused...

thanks

[Brag]

First of all don't confuse course with bearings.The relative bearing to any object is the direction to which you turn to face it. If it is directly in front of your bow, the relative bearing will be 000 or 360.

If it is off your port side, the relative bearing will be 270
Abaft your stern, it will be 180
Starboard beam 090.

A true bearing would be the relative bearing drawn on the chart and measured from north.

This should clear the confusion (I hope) :D

[Sailor Steve]

Relative bearing is the target's bearing in relationship to you, no matter what direction you're heading. If the lookout says the target is at 301, then using the UZO to look at him will show a bearing of...301!

I understand the rest of the procedure well enough to know what it means, but I'm afraid any explanation I can give beyond what I've already done will only make you more confused. Someone with the knowledge to do it right will be along presently.

[flag4]

ok. how does olc arrive at the figure of 59 degrees - i can only assume he has subtrated 301 from 360 ??

this i can understand: 360 -
301
059

he draws with his protractor a line from his course, clicking on his boat then reaching out with line to position of ship = 59 degrees.

now for some reason i can not seem to get this to work for me: if i see a ship at 265 degrees then this must mean it is 95 degrees relative to me, yes ?

and yet when i try this on the chart i get a completly different figure ?

im lost...
im wondering what im doing wrong ?

[geosub1978]

hi hunters

could someone please explain 'course relative to bearing' :damn:

if a ship is spotted at 301 degrees, what is the bearing relative to me ?

im watching olc's tutorial and trying to understand the bit where he is plotting the course of the ship, and, he says its 59 degrees relative to his course.

ive treid to work this out on my own and it doesnt add up, coz i know something happens when a ship is moving away from, like, subtracting the 301 from 360 which gives 59. and yet this doent always seem to work.

ive tried it with numerous different courses and i can not get the maths to work - and i have to say its driving me nuts: is there a formula for this ?

ie; when a ship is coming to me and when a ship is moving away.
im very confused...

thanks

OK! Let's make something clear.

It depents on how you BEGIN counting the bearing of the target.

A circle has 360 degrees.

The NORTH direction is always at 000 degrees. TRUE bearings and TRUE coarses are always counted from NORTH. So if target's TRUE bearing is 301, this means that the direction of the target is 301 degrees (counting right) from NORTH. This is indepentend from submarines coarse.

However, if you want to measure the direction of the target relative to your BOW, then you have to regard as 000 the direction your bow points! So if a target's RELATIVE bearing is 301, this means that the direction of the target is 301 degrees (counting right again) from SUBMARINE'S BOW!

So! 301 degrees relative bearing is 301 degrees RIGHT from you coarse.

Your bow can be regarded as the begining of a circle (000 degrees) OR the end of a circle (360 degrees).

If you regard you bow the end of the circle, then if you substruct 301 degrees from the end (360-301=59) you have target's RELATIVE bearing 59 degrees LEFT from your bow!

That's all!

[flag4]

hi hunters

could someone please explain 'course relative to bearing' :damn:

if a ship is spotted at 301 degrees, what is the bearing relative to me ?

im watching olc's tutorial and trying to understand the bit where he is plotting the course of the ship, and, he says its 59 degrees relative to his course.

ive treid to work this out on my own and it doesnt add up, coz i know something happens when a ship is moving away from, like, subtracting the 301 from 360 which gives 59. and yet this doent always seem to work.

ive tried it with numerous different courses and i can not get the maths to work - and i have to say its driving me nuts: is there a formula for this ?

ie; when a ship is coming to me and when a ship is moving away.
im very confused...

thanks

OK! Let's begin with coarse

Let's say your coarse is 125. This means you are 125 degrees right from 000 degrees which ALWAYS points NORTH!. This is your TRUE coarse.

If a target is 25 degrees LEFT from your coarse this means that target's TRUE bearing is 125-25= 100 degrees. So, 100 is target's TRUE bearing.

If a target is 25 degrees RIGHT from your coarse this means that target's TRUE bearing is 125+25=150. So, 150 is target's TRUE bearing.

However, if you regard that the direction that you bow points is 000 (nomatter what TRUE coarse is), this is regarded as your RELATIVE coarse. Then, if a target is 25 degrees LEFT from you bow, this means that target's RELATIVE bearing is 25 degrees LEFT. If the target is 25 degrees RIGHT from your bow, this means that target's RELATIVE bearing is 25 degrees RIGHT.

That' all!

now wait a minute, this is begining to make sense, the left and right stuff + and -, this is where im going wrong; so, what happens if the ship is heading away from me ? does left and right still apply

[flag4]

its this i dont get;

However, if you regard that the direction that you bow points is 000 (nomatter what TRUE coarse is), this is regarded as your RELATIVE coarse. Then, if a target is 25 degrees LEFT from you bow, this means that target's RELATIVE bearing is 25 degrees LEFT. If the target is 25 degrees RIGHT from your bow, this means that target's RELATIVE bearing is 25 degrees RIGHT.

at the moment i am looking at a circular protractor with the spinning arrow in the middle, a bit like this with the numbers going in opposite directions

http://www1.istockphoto.com/file_thumbview_approve/1547561/2/istockphoto_1547561_matter_of_degree_circular_prot ractor.jpg

i can turn the arrow to see the bearing - it helps but i need to understand more of what YOU are saying !!

[flag4]

thank you geosub

i've printed your posts off and will be reading them AND rereading them !!

i feel a bit closer to understanding it now

cheers :up:

[Firebird]

Look at that outer circle. Your submarine's bow is pointed in the direction of 0, so it's going left on that picture: <------<.

If you now spot a target 'bearing 25°', that means it's currently at 25° on that outer circle, so a bit to your right.

If you spot a target bearing 335° it's a bit to your left as you can see. The degrees are always counted clockwise starting from 0.

Now keep this in mind :). All of this is about relative bearing. Relative to what? To your submarine's bow, which is at 0°.

Introducing 'course': a ship is moving on a certain course, again expressed in degrees. Take that same circle, but rotate it clockwise one quarter so that the 0 on the outer circle is pointing upwards (north). Now you can see what each course means. If your submarine is on course 0°, it's going north (up). If it's on course 90° it's going due east, 180° south and 270° west. If a ship is reported going north-east, it's moving at a course of approximately 45° (up and right, diagonally). Don't forget, 0° is always pointing north (up) when talking about course, while 0° is always pointing to your submarine's bow when you're talking about bearing.

Now combine the two: your submarine might be on a course of 90° (due east >---->), and spot a target at bearing 270°. That means that when you look north (which is to the left of your bow), you'll see that target.

[geosub1978]

so, what happens if the ship is heading away from me ? does left and right still apply

NO!!!!!!

It has nothing to do!

For instant bearing (one bearing value), target's motion has nothing to do! Instantly, target is regarded as a motionless point, for one bearing measurement!

Bearing's deviation as time flows (bearing rate) has to do with SUBMARINE'S coarse speed, TARGET'S coarse speed and SUBMARINE to TARGET distance.
But this is another big chapter!

[Pisces]

now wait a minute, this is begining to make sense, the left and right stuff + and -, this is where im going wrong; so, what happens if the ship is heading away from me ? does left and right still applyWhen you see someone walking on the street on your left-side (relative bearing between 180 and 360), you don't turn your head from side-to-side (bearing) any bit differently whether he or she is moving away or comming closer to you (which is due to the 'Angle On that person's Belly' ;) ).

The problem with this day-to-day analogy, is that you are physically not able to rotate your head beyond your rear, like periscopes can do, and have to turn it in a counterclockwise fashion from your front.


p.s. maybe it helps if you post a screenshot showing how your angle plotting doesn't match.

[JohnnyBlaze]

I'm not sure If I'm answering the correct question, but if you want to know the targets true bearing from north you have to add your own course and target bearing.
lets say your course is 045 and target's bearing is 330 from your bow.
45+330 = 375
And when the true bearing from north is over 360, you subract 360 from the value
45+330 = 375-360 = 15 This is the true bearing from north

Now you can draw a bearing from your sub at the nav map to bearing 15 from north.

This is the method I've been using when drawing an intercept course on the nav map

Hope this helps

[flag4]

thanks for the explanations.

i'm sorry Pisces i cant follow what you have tried to explain.....:damn:


but i think i am begining to understand JohnnyBlaze.

i was at a freinds house today and i discoverd he knew something about bearing and course in terms of flying a plane.
we were'nt supposed to be doing bearing but it got him so interested in it we both ended up standing in the middle of his room pushing back tables and chairs, with me as the u boat and him as the ship. he then tried to expalin what i didnt understand by moving around me - calling out bearing values as he went :rotfl:

i dont know what his wife thought but it must have a been a odd sight for any one watching two men doing a strange dance in the front room which looks out directly onto the pavement and road. he too talked about adding and subtracting according to left and right of the compass.

i've written notes down on paper while i was there so as to mull over later on today sat watching the boats escape me on the Naval Torpedo Lesson.
i feel like such a durr not being able to get it - but i hope to soon

thanks for your help, i'll let you all know when i get it :up:

[JohnnyBlaze]

It is our pleasure to help out anyone in need. :yep:

I wish you good luck and hope that you graduate from the academy soon :up:

[Catfish]

Hello,
hope i don't bore you :hmm:
This is really simple, but you have to get used to it.
For developing a torpedo solution the absolut bearing (from North or whatever) is not important. This is because all the torpedo (or better the settings) need to know is where the enemy ship is relatively to you own U-boat. So your boat is the
center of everything.

Absoute heading (on the chart): This never changes, altogether there are 360 degrees around a circle, North is 000 or 360 degrees (same here), East is 090 or 90 degrees, South is 180 degrees and West is 270 degrees. Always.
(Hrrm, there may be magnetic deviations, but not in SH3, and even then you have a gyrocompass that does not depend on magnetism.)

If you are heading Northnortheast the absolute course on the map you travel at what course ? Northeast would be the middle from 0 to 90, so 45 degrees. Northnortheast is two parts north and one part East, so you travel at 030 or 30 degrees.

OK, we just said this does not matter setting up a torpedo solution :lol:

Standing on your U-boat's conning tower this boat becomes your center of the universe. Your bow always points to zero, or 0, or 000, or 360 degrees. Imagine standing on a ship's deck and you see something to your right. You could yell "something on the right", but unless it is not at 090 degrees this is not very exact.

Were you in a plane you would yell something like "enemy at 3 o'clock high" which would be an enemy plane at 090 degrees and higher relative to your own plane (which's nose again would be 12 o'clock). However we are at sea, and us mariners use the 360 degrees circle, not the 12 o'clock circle, and certainly do not bother
with high or low ;)

So if a watch wants you to tell something like a sighted ship he takes the U-boat as the reference system, and tells you the position of the other ship relatively to your own boat's course - beginning to count at the bow with 0 until the sighted ship appears. This is the course of sight relatively to you ship, or better relatively to your ship's course.
What is confusing here is that they talk about "course". You have to understand that every angle or direction is called a "course" on a ship. If a ship appears to your left your watch will shout "ship at 270 degrees!", and he could as well shout
"ship course 270 degrees!". The enemy ship's own real course does not have anyting to do with it.

Hmm, does that help ?

Greetings,
Catfish

[flag4]

hi Catfish

thank you for your explanation. i understand the clock affect as the degrees go round the compass; if my WO calls out ship spotted at 90 degrees i know he is on my right which ever way im heading...

what im struggling with is demonstarted in OLC's tutorial when he plots a course parralell to a ship on his left. WO calls out ship spotted bla bla bla degrees. ( i cant remember the exact course im at a different computer..)

he then enters the information on to his nav map and - this is the bit im stuck with - draws a line from his boat to the ship using his protractor, clicking first on his course then his u boat then extends this line out towards the ship to about two thousands yards, where his WO spotted it

there is an angle he comes up with like 53 degrees from his boat to the ship - this then pin points the ship.
and if he didnt have his ship contacts turned on ( the little black squares.) the ship would be at the end of this line/angle.

do you understand me ?

how does he arrive at this angle. its something like 360 - degree of spotted ship = 53 degrees.
and i believe this changes whether a ship is port or starboard. its either subtract or add.

tell me what you think - do you understand me? if you watch OLC's tutorial you will see what i mean - i may not have expalined it very well.

thanks
flag4

[bert8for3]

From what you're saying, I think OLC must have been marking a reported bearing to the target using the protractor tool. The tool unfortunately does not mark bearings in straightforward 0 deg through 360 deg, but rather in 0 to 180 going starboard (right) and 0 to 180 going port (left). If he marked the protractor line out on 53 deg to port (left), the reported bearing must have been 307 deg, which for using the protractor (for port or left side bearings) has to be translated as 360-307=53. If the bearing was starboard (right) it would have been reported simply as 053 deg and you would just lay off 53 deg (right) with the protractor.

[wizardmatt]

Hi OP.
This link could be helpful:

http://www.paulwasserman.net/SHIII/

It is a tutorial on charting and plotting, as suggested by the "newbie guide" stickied thread above. Ive found it VERY helpful; its described somewhere as "essential reading", and it addresses exactly the issues youre talking about, with helpful diagrams.
you can if you wish download the guide: HOWEVER, the last time i tried the link for the download at wazoo's site, it didnt work, so i just googled something like "wazoo sh3 manual plotting charting guide download" - i now have it in my documents!

EDIT: here you go:

www.finael.fr/sh3/charge/charting_&_targeting.doc

good luck! :up:

[flag4]

bert8for3

you understood me !! :up:

i kind of see what you mean. it will take a while to use it smoothly with out doubt or cock-ups but i will get there.

and thanks to you wizardmatt i will be able to study it in a bit more depth.
i know the navigation tools have developed quite a lot since wassermans tutorial but i think i can suss out whats relavent to using olc's today !!

many thanks for your help.
flag4

[wizardmatt]

youre welcome :up: