Contact Intercept

sixcoins · 08-30-12, 07:20 PM

Hello Sailors.

I'm having a problem with intercepting contacts. Spending a lot of time studying and trying it out, but I keep coming up short.

First, let me say I've done my studying. I'm reading the tutorials and practicing in game.

Right now, in particular, I'm using this tutorial. It seems to be all that I need for now, and this is the one I want to master. I'll add more tools to my bag later for certain, but right now my question is based on this method.

I'm using thread The Hunt: An illustrated example of how to sink a ship.

My problem comes up when it's time to draw the circle. Just for the sake of conversation, I'm using a scale factor of 10. If My target is going 9 knots, then my line showing his track is 90knots. Therefore, if my speed is 12, my compass circle is using a radius of 120.

The instructions i'm following for this part of the procedure is as follows...

So you draw a circle, centered at the end of the ruler measurement you did in step 3, with a radius of 160 mks... why 160 mks? because in step three you chose to represent each knot by 10 mks, remember? (If in step three you'de had measured 6 kms for the 6 knots you would now be drawing a circle radius of 16 kms for 16 knots, and so on). Let's look at your circle
http://static.flickr.com/36/93898889_aa6ce333c7_o.jpg
Take special notice of were the circle cuts the line formed from your u-boat to the contact.

This is where my problem comes in .... My circle never intersects the line formed from my u-boat to the contact. My circle is always waaaaay too big. It's the correct size according to the tutorial, which I understand it should be u-boat speed x 10. (10 is the multiplier I used when drawing the target ships course) However, even though it seems to be the correct numbers, it doesn't create any useful information. It's just a circle around the whole shebang.

I really want to be able to do this method. I won't be able to do it until I understand whatever it is that I'm overlooking.

Can anyone see my error? I can't.

Thanks in advance.

Six

Pisces · 08-30-12, 07:58 PM

Maybe that's because there isn't one. You're not doing anything wrong I think so far. The circle intersects the line between you and the contact in the vicinity of the gridnumber AM24. Give me a moment while I upload my modified image.

The colors are in reference to Kylania's image I showed in another thread.

The light green protractor leg pointing ahead of the contact is the way to go.

Link to Kylania's image: http://www.kylania.com/sh3/Intercept_Plotting.png

sixcoins · 08-30-12, 08:15 PM

Thanks again Pisces.

I'll keep practicing it. I'm not sure why my circle keeps being bigger than my entire plot... Maybe I should be extending lines out further...

In my picture, it's all in one area inside one sector... In your picture, and in her picture, its over an area of about 4 sectors.

I guess I need to scale down a bit with the plotting tools, or use more of the map and draw longer lines....

Maybe that's why I'm having a hard time. Perhaps my common sense hasn't quite kicked in yet.

I'll keep trying, and thanks for all your help.

sixcoins · 08-30-12, 09:03 PM

Ok.... I have an example for you, Pisces. I wanted to show you what messes I'm making over here.

Here is a picture of MY plot.....

Clearly I'm not paying attention to something that's important, but I just don't know what it is.

Clearly my circle is too big, but it does follow the instructions of the tutorial.

I'm thinking that there's some bonehead common sense procedure that every captain worth his weight in salt already knows. Except me.

Small Edit..... I DID scale my circle down until it cut through the line between myself and the contact... and when that happened, the circle ended up cutting through that line in 2 locations. And the distance of the circle was not any factor of 12. So.... that confused me even more.

Thanks again, in advance, for any help you can provide.

Six.

complutum · 08-30-12, 09:44 PM

I think that your problem is your making circle radious with own speed by factor instead of use this value for circle diameter. in your example with own speed 12 knots he circle radious must be 60km that means 120km diameter.

sixcoins · 08-30-12, 09:51 PM

Quote:

Originally Posted by complutum

I think that your problem is your making circle radious with own speed by factor instead of use this value for circle diameter. in your example with own speed 12 knots he circle radious must be 60km that means 120km diameter.

Possibly, but In the tutorial photo, they did use a factor of 10 for 16 knots, and the radius was 160Km. (and in that example, the target line was also 60 kilometers).

Tricky.

Pisces · 08-31-12, 08:28 AM

Quote:

Originally Posted by complutum

I think that your problem is your making circle radious with own speed by factor instead of use this value for circle diameter. in your example with own speed 12 knots he circle radious must be 60km that means 120km diameter.

No no, definitely not diameter. The edge of the circle represents the collection of courses at the defined own speed. It has to be the radius that must correspond to the speed. The target speed being 12 or 120, while the contact speed is (assumed) 6 or 60, thus halve of it, is entirely coincidence.

Pisces · 08-31-12, 08:20 AM

Quote:

Originally Posted by sixcoins

Ok.... I have an example for you, Pisces. I wanted to show you what messes I'm making over here.

Here is a picture of MY plot.....

Clearly I'm not paying attention to something that's important, but I just don't know what it is.

Clearly my circle is too big, but it does follow the instructions of the tutorial.

I'm thinking that there's some bonehead common sense procedure that every captain worth his weight in salt already knows. Except me.

Small Edit..... I DID scale my circle down until it cut through the line between myself and the contact... and when that happened, the circle ended up cutting through that line in 2 locations. And the distance of the circle was not any factor of 12. So.... that confused me even more.

Thanks again, in advance, for any help you can provide.

Six.

Yes, I see what you are missing. Due to your multiplication by 10 the red circle encompasses the entire distance from you to the target. The easy solution would be not to enlarge by 10, but just draw 1 for 1. (like Sublynx did in the later message with multiple images: #9, but that was apparently 3 for 1 )

Alternatively, if you didn't want to redraw the whole thing. The propper course of action (no pun) would be to extend the line between the target and you beyond your actual location. This is allowed because the line between you and the contact is supposed to be a bearingline extending into infinity. It shouldn't really stop where you are. The length of it is of no concern for the intercept course. Just as long as that green protractor angle has the corner at where you are.

You are forgiven, for it wasn't really explained in the Hunt thread. See the following image:

sublynx · 08-31-12, 08:56 AM

Quote:

Originally Posted by Pisces

Alternatively, if you didn't want to redraw the whole thing. The propper course of action (no pun) would be to extend the line between the target and you beyond your actual location. This is allowed because the line between you and the contact is supposed to be a bearingline extending into infinity. It shouldn't really stop where you are. The length of it is of no concern for the intercept course. Just as long as that green protractor angle has the corner at where you are.

Wow I didn't think about that solution to the problem at all. Very clever, and makes sense now that you point out the fact to us

Pisces · 08-31-12, 09:59 AM

Quote:

Originally Posted by sixcoins

...
Small Edit..... I DID scale my circle down until it cut through the line between myself and the contact... and when that happened, the circle ended up cutting through that line in 2 locations. ...

2 intersections is indeed possible if your chosen intercept speed is close to the minimum required. The minimum speed is when the red circle touches the (infinite) black bearing line between you and the target. Another way to draw it is to drag the corner of the yellow protractor along the black line until it is 90 degrees. You have to go faster than that, or you will never meet!

The closer intersection of the red circle and the black line is the slower way to close. The course that results is actually having you trying to get away from him along the bearing line. But his closing outways your moving away. Always use the furthest intersection.

Quote:

...
And the distance of the circle was not any factor of 12. So.... that confused me even more.

That's why I suggest not to multiply with odd-lot numbers, 2,3,4,5,6,7... . Stick to 1, or 10. And extend that bearing line if needed. No brain-burning by multiplying is required.

Pisces · 08-30-12, 08:18 PM

Hmm, now I noticed this image was taken directly from the Hunt thread.

Why don't you make a screen dump of your own map, and upload that? Then we can see what you are doing wrong. Instead of how Dantenoc did it.

CaliEs · 08-31-12, 05:43 PM

Quote:

Originally Posted by Pisces

Link to Kylania's image: http://www.kylania.com/sh3/Intercept_Plotting.png

This drawing make only sense when the blue line is measured as 16.0, not 6 as indicated.

Pisces · 08-31-12, 07:33 PM

Quote:

Originally Posted by CaliEs

This drawing make only sense when the blue line is measured as 16.0, not 6 as indicated.

I admit that it doesn't look properly to scale. But the steps are geometrically correct.

TorpX · 09-04-12, 12:00 AM

I haven't used this method, so I decided to break out a pencil and paper and take a closer look at it. For some reason my brain learns better from graphite on paper, than illuminated pixels on a computer screen.

I must admit I like this method, now that I understand it. However, there is a simpler alternative that will suffice in many cases. This is the Normal Approach Course. I'm guessing some here already know what this is, but I thought I'd outline it for those who don't.

The Normal Approach Course gets it's name from the fact that you are taking a course normal (perpendicular) to the target. That is, if the target is on a closing track, the true bearing of the target is 25 deg., and it is drawing off to the South, you would steer 115 deg. true. You don't need to know the distance, exact course, or speed of the target. (This makes it ideal in situations where you have only a sound contact.) By the way the situation develops, you will know if a interception is possible:

Case 1- You are gaining bearing on the target.
That is the true bearing of the target goes from 25 to 24 to 23 deg., etc., etc. You can maintain your speed and reach the target's track ahead of it. You can reduce speed to intercept. Or, you can maintain speed and cut into the target's track to intercept sooner.

Case 2- True bearing of the target is constant.
If you and the target hold course and speed, an interception is assured. (You are on a collision course!)

Case 3- You are losing bearing on the target. That is, the target's bearing is going from 25 to 26 to 27 deg., etc. In this case an interception at this speed is impossible. You must either increase speed, or consider weather it is advisable to continue the approach (it is sometimes possible to get close enough for a torpedo attack even though an "interception" does not take place).

The key element of the Normal Approach Course is that it allows an intercept at a minimum of speed. Another critical element is that it is only relevant for targets on a closing track (moving closer to you). Following a Normal Approach Course on a target that is already moving away from you will avail you nothing. In this case you would be better off to follow the method already explained in this thread.

Pisces · 09-04-12, 11:33 AM

Quote:

Originally Posted by TorpX

I haven't used this method, so I decided to break out a pencil and paper and take a closer look at it. For some reason my brain learns better from graphite on paper, than illuminated pixels on a computer screen.

I must admit I like this method, now that I understand it. However, there is a simpler alternative that will suffice in many cases. This is the Normal Approach Course. I'm guessing some here already know what this is, but I thought I'd outline it for those who don't.

...

This is definitely the best solution if you are submerged, and slow. It does make the intercept take quite a while though. You'll make the target do all the closing of the gap. So turning into the target whenever his bearing is changing towards your rear is very advisable to reduce the time. If all you have is a bearing, then this is the simplest way to go. With a periscope view the bearing change is even more easier to see.

08-30-12, 07:20 PM	#1
sixcoins Seaman Join Date: Nov 2011 Posts: 40 Downloads: 6 Uploads: 0	Contact Intercept Hello Sailors. I'm having a problem with intercepting contacts. Spending a lot of time studying and trying it out, but I keep coming up short. First, let me say I've done my studying. I'm reading the tutorials and practicing in game. Right now, in particular, I'm using this tutorial. It seems to be all that I need for now, and this is the one I want to master. I'll add more tools to my bag later for certain, but right now my question is based on this method. I'm using thread The Hunt: An illustrated example of how to sink a ship. My problem comes up when it's time to draw the circle. Just for the sake of conversation, I'm using a scale factor of 10. If My target is going 9 knots, then my line showing his track is 90knots. Therefore, if my speed is 12, my compass circle is using a radius of 120. The instructions i'm following for this part of the procedure is as follows... So you draw a circle, centered at the end of the ruler measurement you did in step 3, with a radius of 160 mks... why 160 mks? because in step three you chose to represent each knot by 10 mks, remember? (If in step three you'de had measured 6 kms for the 6 knots you would now be drawing a circle radius of 16 kms for 16 knots, and so on). Let's look at your circle http://static.flickr.com/36/93898889_aa6ce333c7_o.jpg Take special notice of were the circle cuts the line formed from your u-boat to the contact. This is where my problem comes in .... My circle never intersects the line formed from my u-boat to the contact. My circle is always waaaaay too big. It's the correct size according to the tutorial, which I understand it should be u-boat speed x 10. (10 is the multiplier I used when drawing the target ships course) However, even though it seems to be the correct numbers, it doesn't create any useful information. It's just a circle around the whole shebang. I really want to be able to do this method. I won't be able to do it until I understand whatever it is that I'm overlooking. Can anyone see my error? I can't. Thanks in advance. Six

09-04-12, 12:00 AM	#14
TorpX Silent Hunter Join Date: Sep 2010 Posts: 3,975 Downloads: 153 Uploads: 11	I haven't used this method, so I decided to break out a pencil and paper and take a closer look at it. For some reason my brain learns better from graphite on paper, than illuminated pixels on a computer screen. I must admit I like this method, now that I understand it. However, there is a simpler alternative that will suffice in many cases. This is the Normal Approach Course. I'm guessing some here already know what this is, but I thought I'd outline it for those who don't. The Normal Approach Course gets it's name from the fact that you are taking a course normal (perpendicular) to the target. That is, if the target is on a closing track, the true bearing of the target is 25 deg., and it is drawing off to the South, you would steer 115 deg. true. You don't need to know the distance, exact course, or speed of the target. (This makes it ideal in situations where you have only a sound contact.) By the way the situation develops, you will know if a interception is possible: Case 1- You are gaining bearing on the target. That is the true bearing of the target goes from 25 to 24 to 23 deg., etc., etc. You can maintain your speed and reach the target's track ahead of it. You can reduce speed to intercept. Or, you can maintain speed and cut into the target's track to intercept sooner. Case 2- True bearing of the target is constant. If you and the target hold course and speed, an interception is assured. (You are on a collision course!) Case 3- You are losing bearing on the target. That is, the target's bearing is going from 25 to 26 to 27 deg., etc. In this case an interception at this speed is impossible. You must either increase speed, or consider weather it is advisable to continue the approach (it is sometimes possible to get close enough for a torpedo attack even though an "interception" does not take place). The key element of the Normal Approach Course is that it allows an intercept at a minimum of speed. Another critical element is that it is only relevant for targets on a closing track (moving closer to you). Following a Normal Approach Course on a target that is already moving away from you will avail you nothing. In this case you would be better off to follow the method already explained in this thread.

08-30-12, 07:58 PM	#2
Pisces Silent Hunter Join Date: Dec 2004 Location: AN9771 Posts: 4,904 Downloads: 304 Uploads: 0	Maybe that's because there isn't one. You're not doing anything wrong I think so far. The circle intersects the line between you and the contact in the vicinity of the gridnumber AM24. Give me a moment while I upload my modified image. The colors are in reference to Kylania's image I showed in another thread. The light green protractor leg pointing ahead of the contact is the way to go. Link to Kylania's image: http://www.kylania.com/sh3/Intercept_Plotting.png

08-30-12, 08:15 PM	#3
sixcoins Seaman Join Date: Nov 2011 Posts: 40 Downloads: 6 Uploads: 0	Thanks again Pisces. I'll keep practicing it. I'm not sure why my circle keeps being bigger than my entire plot... Maybe I should be extending lines out further... In my picture, it's all in one area inside one sector... In your picture, and in her picture, its over an area of about 4 sectors. I guess I need to scale down a bit with the plotting tools, or use more of the map and draw longer lines.... Maybe that's why I'm having a hard time. Perhaps my common sense hasn't quite kicked in yet. I'll keep trying, and thanks for all your help.

08-30-12, 09:03 PM	#4
sixcoins Seaman Join Date: Nov 2011 Posts: 40 Downloads: 6 Uploads: 0	Ok.... I have an example for you, Pisces. I wanted to show you what messes I'm making over here. Here is a picture of MY plot..... Clearly I'm not paying attention to something that's important, but I just don't know what it is. Clearly my circle is too big, but it does follow the instructions of the tutorial. I'm thinking that there's some bonehead common sense procedure that every captain worth his weight in salt already knows. Except me. Small Edit..... I DID scale my circle down until it cut through the line between myself and the contact... and when that happened, the circle ended up cutting through that line in 2 locations. And the distance of the circle was not any factor of 12. So.... that confused me even more. Thanks again, in advance, for any help you can provide. Six.

08-30-12, 09:44 PM	#5
complutum Torpedoman Join Date: Aug 2010 Location: Spain Posts: 118 Downloads: 387 Uploads: 0	I think that your problem is your making circle radious with own speed by factor instead of use this value for circle diameter. in your example with own speed 12 knots he circle radious must be 60km that means 120km diameter.

08-30-12, 08:18 PM	#11
Pisces Silent Hunter Join Date: Dec 2004 Location: AN9771 Posts: 4,904 Downloads: 304 Uploads: 0	Hmm, now I noticed this image was taken directly from the Hunt thread. Why don't you make a screen dump of your own map, and upload that? Then we can see what you are doing wrong. Instead of how Dantenoc did it.