SUBSIM Radio Room Forums - View Single Post - Determining course of contact that is "smoke on the horizon"

Jaystew · 06-15-14, 06:42 PM

Suppose you are heading due north and your heading is therefore 000. Take the contact's bearing from your ship. Suppose its at Bearing 060. If you want to make an intercept, first start with pure pursuit by changing your heading to that of the contact. Make heading 060.

There are 3 possible outcomes. The target can be heading...
Directly toward you (Unlikely)
Directly away from you (Unlikely)
On a different course than your course. (Most likely)

Once on that heading and at a steady speed. 10 kts is a good long range intercept speed. Note the time exactly. Note your position on the map exactly and note the relative bearing of your target exactly. (Be aware you do not need to know exactly where you are on the ocean only exactly where you are relative to each tracking measurement you are about to make.)

Make an X on the map noting your subs position. Draw a line of bearing out from that spot and extend it 30km.

At 2 minutes note the apparent bearing of the ship on the horizon. If the ship is to the left or right of your bow you can rule out that it is heading directly towards or away from you.

If the contact is still on bearing 000 and simply smaller or you've lost contact it was moving faster than you and opening distance. If the contact is larger but on the same bearing are your pursuit it is closing. It have may detected you and be on an intercept course. Likely a warship. The last possibility is that it is moving directly away but slower than you sub so you are gaining on it.

In the most likely situation the contact will be either right or left of the bow a few degrees. Remember you matched your heading to the bearing of the contact and are on heading 060. Suppose the contact is now at bearing 002.

The only thing you can conclude is that the target is heading somewhere between 060 and 240 and that it is moving.

So again at 2 minutes note that the contact is now at 062. Maintain your heading of 060 along the original bearing. Measure out where your sub would be from the original X and make a new X. From this new X draw a line of bearing out 30km.

Repeat the process at 4 min and again at 6 min. As you take more bearing measurements. Assuming the target maintains a straight course you will very soon determine the range within a few hundred meters. You will also be able to determine the targets course within 10 degrees.

That should set you up with where you need to go in the beginning.

06-15-14, 06:42 PM	#2
Jaystew Sparky Join Date: Apr 2013 Posts: 151 Downloads: 50 Uploads: 0	Suppose you are heading due north and your heading is therefore 000. Take the contact's bearing from your ship. Suppose its at Bearing 060. If you want to make an intercept, first start with pure pursuit by changing your heading to that of the contact. Make heading 060. There are 3 possible outcomes. The target can be heading... Directly toward you (Unlikely) Directly away from you (Unlikely) On a different course than your course. (Most likely) Once on that heading and at a steady speed. 10 kts is a good long range intercept speed. Note the time exactly. Note your position on the map exactly and note the relative bearing of your target exactly. (Be aware you do not need to know exactly where you are on the ocean only exactly where you are relative to each tracking measurement you are about to make.) Make an X on the map noting your subs position. Draw a line of bearing out from that spot and extend it 30km. At 2 minutes note the apparent bearing of the ship on the horizon. If the ship is to the left or right of your bow you can rule out that it is heading directly towards or away from you. If the contact is still on bearing 000 and simply smaller or you've lost contact it was moving faster than you and opening distance. If the contact is larger but on the same bearing are your pursuit it is closing. It have may detected you and be on an intercept course. Likely a warship. The last possibility is that it is moving directly away but slower than you sub so you are gaining on it. In the most likely situation the contact will be either right or left of the bow a few degrees. Remember you matched your heading to the bearing of the contact and are on heading 060. Suppose the contact is now at bearing 002. The only thing you can conclude is that the target is heading somewhere between 060 and 240 and that it is moving. So again at 2 minutes note that the contact is now at 062. Maintain your heading of 060 along the original bearing. Measure out where your sub would be from the original X and make a new X. From this new X draw a line of bearing out 30km. Repeat the process at 4 min and again at 6 min. As you take more bearing measurements. Assuming the target maintains a straight course you will very soon determine the range within a few hundred meters. You will also be able to determine the targets course within 10 degrees. That should set you up with where you need to go in the beginning.