How to guess speed of a ship?

GertFroebe_neu · 01-11-11, 10:09 AM

Hello!

I am playing SH5 now for a while and I am always practicing manual targeting. Most of the time it works really fine, but I do not really know how to guess the speed of my target. I do not like to use the stadimeter for this, because for a german u-boat it is historically incorrect and it doesn't even work that good.

Is there a trick to guess or calculate the speed?

cheers
Marc

Walle · 01-11-11, 11:17 AM

I like the 3 minute rule, or actually the 3:15 rule (more accurate).

Make a mark on your target ships position and immediately start the chronometer (if you're zoomed in close and want precision, make the mark a little ahead of the ships stern or bow and start the chrono when the ship passes the mark). Wait 3 minutes and 15 seconds, and make a new mark (but don't stop the chrono). Measure the distance (i prefer the compass rather than the ruler). Now, the speed in knots is the distance in km multiplied by 10. I.e, the ship moved 1450 meter, then the speed is 14.5 knots.

Since you didn't stop the chrono at 3:15, make another mark at 6:30 and multiply the distance by 5 to get an even more accurate reading.

If you're using imperial instead of metric units, just multiply by ten and add a tenth, since a yard is roughly 0.9 meters.

Redlance88 · 01-11-11, 11:46 AM

mostly it comes down to what other information your using to track and make various solution guesses about the ship that you are tracking. what you need to figure out a ships speed is to know how far it has traveled in a certain amount of time... D/T = speed. for silent hunter distance is in either meters or nautical miles. and time is in seconds ( not very useful) min or hours. knots are nautical miles /per hour. so if you have the ability to accurately locate the ship at two different times, you can measure or calculate the distance traveled for that specific amount of time and get the speed of the ship from that information.
Lost yet? in the game there are several ways to get this information and they vary in how historically accurate they are. but in simplest terms you have to time the ship your tracking and see how far it goes in the time you watch it. now this is where it depends on how you play the game and what information you have to work with. if you can see the contact on the map you can just put a mark on it , hit the u key start the stop watch , and a min later put a mark on where the ship has moved to, and grab the ruler and see how far the ship has moved in 1 min. this distance will be in meters and the time is one min so it will have moved say 154 m in one min. or (154m X 60 Min ) 9240 m / hour. one knot is 1852 m per hour so if you divide 9240 by 1852 you get 4.98... or as close that makes no differance 5 knots / hour. I hope that was more helpful than confusing, but like I said without knowing things like if you have show enemy contacts on the map turned on or things like that I cant be more specific on what your trying to do. other than the basics of speed = distance over time. and that a knot per hour is = to 1852 meters per hour. or about 31 meters per min.

Trevally. · 01-11-11, 12:44 PM

If you have a AOBF then see this

http://www.subsim.com/radioroom/show...3&postcount=37

GertFroebe_neu · 01-11-11, 01:07 PM

Hello!

Thanks! Your postings were very helpful. Actually I thought there might be a gamefunction that would help with this, but I don't mind some calculating.

How did the german uboat-commanders guess the speed? They did not have a selfupdating map

?

cheers
Marc

GertFroebe_neu · 01-11-11, 01:13 PM

Quote:

Originally Posted by Trevally.

If you have a AOBF then see this

http://www.subsim.com/radioroom/show...3&postcount=37

Also very interesting! I guess it does this only applies when the ship ist moving exactly in front of my periscope, passing by. So I got to get ahead of the ship again to attack it, right?

cheers
Marc

PS.: The AOBF can not be moved. Same Problem with the Attack disc!

Walle · 01-11-11, 01:37 PM

Well, it's really just a combination of different basic navigation techniques.

There's several different ways to know the position of OwnShip for example.

You could either get a "fix" by means of taking bearings to different navigational aids (lighthouses e.t.c.) or landmarks (church towers, tall buildings, special cliffs, e.t.c.). Taking two bearings and drawing them as lines, you would be near where the lines intersect. Taking a third bearing increases the precision.

Another way is to use celestial objects. Then you would have to take inclination readings to at least two objects in different directions. This technique involves a lot of math, since you also need to calculate the inclinations for the date and time you take the reading. The absolutely simplest and crudest form of navigating "by the stars" is having a stick that you hold out against north. As long as the ends of the stick is at the horizon and the north star, you are on the same latitude. If the star is below the end of the stick (when the other end is at the horizon), you need to go north, if it's too high, you need to go south. This is like the grandgrandfather of the sextant

Then when you have a fix, you would use dead reckoning. I.e. you keep track of the time you go in a certain direction, and at what speed. Then you can draw a line on the chart for the direction, and make markings for distance traveled. When you turn, you make a new line, and so forth.

You need to know your own position to be able to determine the (absolute) position of another ship. The relative position can always be found of course.

To get the position for another ship using the sonar, you would start off by getting his direction by taking three bearings from the sonar at constant interval. Edit: You need to be stationary. (well, actually you don't, but then it get's yet a little bit more advanced.) This will give you the targets course, but not speed nor position. Then you would extrapolate, i.e. add another interval and draw a fourth bearing line. This line is where the target ship will be on at a specific time. But before that, you move your ship, so when it passes the fourth line you take yet another bearing reading from the sonar and draw a line. The target ship will be where that line intersect the "extrapolated" line. Once you know where it is, you also know where it's been (the other three lines) and where, so calculating the speed won't be much of an issue there. I won't get any deeper in this technique, since there's already great tutorials on the forums(fora) covering that.

Using active sonar, you'd just take target ships bearing and distance, no fuzz.
With scope same thing, bearing and distance (using stadimeter). Or time how long it takes the ship to pass the line in the scope, if you know the length of the ship. But it's still the same principle, distance over time.

And then of course, you need to do it twice to get two different positions. Then just calculate the speed as distance divided by time.

Trevally. · 01-11-11, 02:07 PM

Quote:

Originally Posted by GertFroebe_neu

Also very interesting! I guess it does this only applies when the ship ist moving exactly in front of my periscope, passing by. So I got to get ahead of the ship again to attack it, right?

cheers
Marc

PS.: The AOBF can not be moved. Same Problem with the Attack disc!

This just uses the time it takes for a ship to move its own length - so heading is ok - apart from close to a zero AOB or 180 AOB.

The middle ring of the RAOB can be moved by click and drag.

Pisces · 01-11-11, 06:01 PM

Quote:

Originally Posted by GertFroebe_neu

Also very interesting! I guess it does this only applies when the ship ist moving exactly in front of my periscope, passing by. So I got to get ahead of the ship again to attack it, right?

cheers
Marc

PS.: The AOBF can not be moved. Same Problem with the Attack disc!

I just responded about this to Trevaly in his RAOBF thread.

http://www.subsim.com/radioroom/show...&postcount=189

The ship needs to be in your periscope view obviously just before it passes the line. But any AOB between 15 and 165 degrees should present a nice view. Near 0 or 180 is difficult as the ends might be obscured by large structures on deck. Any AOB would take the same time. If you do not have the periscope aimed at 0 or 180 degrees your (even slight) speed affects the results. The solution is to turn to make that happen.

Pisces · 01-11-11, 06:20 PM

Quote:

Originally Posted by Trevally.

If you have a AOBF then see this

http://www.subsim.com/radioroom/show...3&postcount=37

Quote:

Originally Posted by GertFroebe_neu

...
How did the german uboat-commanders guess the speed? They did not have a selfupdating map

?

cheers
Marc

I forgot to respond to that last question. With some periscope models (I don't know if all had it) very similar to this method shown by Trevaly :

http://www.uboot995.homepage.t-onlin...e_im_raum.html

I'm sure the German language is up your alley.

(if you mind, could I entice you to write a translation for this person? My german is barely adequate.
http://www.subsim.com/radioroom/show...8&postcount=14
)

Trevally. · 01-11-11, 06:20 PM

Quote:

Originally Posted by Pisces

If you do not have the periscope aimed at 0 or 180 degrees your (even slight) speed affects the results. The solution is to turn to make that happen.

Good tip, thank Pisces

Matador.es · 01-12-11, 04:14 AM

simple, get the ships lengt, measure the seconds it takes to move from the front to back over the vertical line of your scope. Divide meter by seconds, multiply by, 1.856 and you have speed in knots.

GertFroebe_neu · 01-12-11, 07:07 AM

Quote:

Originally Posted by Pisces

I forgot to respond to that last question. With some periscope models (I don't know if all had it) very similar to this method shown by Trevaly :

http://www.uboot995.homepage.t-onlin...e_im_raum.html

I'm sure the German language is up your alley.

(if you mind, could I entice you to write a translation for this person? My german is barely adequate.
http://www.subsim.com/radioroom/show...8&postcount=14
)

German is no problem. I do even know the websites creator personally.

btw.: If I'd play the game realistically my own speed could not be 0 knots when submerged, because it would be impossible to hold periscope depth very long. But that's just details

Pisces · 01-12-11, 07:24 AM

Quote:

Originally Posted by Matador.es

simple, get the ships lengt, measure the seconds it takes to move from the front to back over the vertical line of your scope. Divide meter by seconds, multiply by, 1.856 and you have speed in knots.

Not quite, 3600/1852= 1.944 (you also have to deal with seconds-to-hours)

But 2 would be easy and good enough for short range shots.

Pisces · 01-12-11, 07:27 AM

Quote:

Originally Posted by GertFroebe_neu

German is no problem. I do even know the websites creator personally.

btw.: If I'd play the game realistically my own speed could not be 0 knots when submerged, because it would be impossible to hold periscope depth very long. But that's just details

Well, what do you know. Small world. Is he also familiar with the SHx series? Or even a member here?

If you don't want to be stationary then read my recent post 9 in this thread. You can move, but requires you turn the bow of the boat in front of the target and set periscope along the uboat centerline (0 or 180 degree bearing).

01-11-11, 10:09 AM	#1
GertFroebe_neu Mate Join Date: Jan 2010 Location: Hamburg Germany Posts: 53 Downloads: 23 Uploads: 0	How to guess speed of a ship? Hello! I am playing SH5 now for a while and I am always practicing manual targeting. Most of the time it works really fine, but I do not really know how to guess the speed of my target. I do not like to use the stadimeter for this, because for a german u-boat it is historically incorrect and it doesn't even work that good. Is there a trick to guess or calculate the speed? cheers Marc

01-11-11, 11:46 AM	#3
Redlance88 Sailor man Join Date: Mar 2010 Posts: 44 Downloads: 67 Uploads: 0	speed of a ship the hard way... mostly it comes down to what other information your using to track and make various solution guesses about the ship that you are tracking. what you need to figure out a ships speed is to know how far it has traveled in a certain amount of time... D/T = speed. for silent hunter distance is in either meters or nautical miles. and time is in seconds ( not very useful) min or hours. knots are nautical miles /per hour. so if you have the ability to accurately locate the ship at two different times, you can measure or calculate the distance traveled for that specific amount of time and get the speed of the ship from that information. Lost yet? in the game there are several ways to get this information and they vary in how historically accurate they are. but in simplest terms you have to time the ship your tracking and see how far it goes in the time you watch it. now this is where it depends on how you play the game and what information you have to work with. if you can see the contact on the map you can just put a mark on it , hit the u key start the stop watch , and a min later put a mark on where the ship has moved to, and grab the ruler and see how far the ship has moved in 1 min. this distance will be in meters and the time is one min so it will have moved say 154 m in one min. or (154m X 60 Min ) 9240 m / hour. one knot is 1852 m per hour so if you divide 9240 by 1852 you get 4.98... or as close that makes no differance 5 knots / hour. I hope that was more helpful than confusing, but like I said without knowing things like if you have show enemy contacts on the map turned on or things like that I cant be more specific on what your trying to do. other than the basics of speed = distance over time. and that a knot per hour is = to 1852 meters per hour. or about 31 meters per min.

01-11-11, 12:44 PM	#4
Trevally. Navy Seal Join Date: Apr 2007 Location: AN1536 (Orkney) Posts: 5,451 Downloads: 166 Uploads: 28	If you have a AOBF then see this http://www.subsim.com/radioroom/show...3&postcount=37 __________________ [SIGPIC][/SIGPIC] Trevally Mods for SH5

01-11-11, 01:37 PM	#7
Walle Watch Join Date: Aug 2009 Posts: 26 Downloads: 7 Uploads: 0	Well, it's really just a combination of different basic navigation techniques. There's several different ways to know the position of OwnShip for example. You could either get a "fix" by means of taking bearings to different navigational aids (lighthouses e.t.c.) or landmarks (church towers, tall buildings, special cliffs, e.t.c.). Taking two bearings and drawing them as lines, you would be near where the lines intersect. Taking a third bearing increases the precision. Another way is to use celestial objects. Then you would have to take inclination readings to at least two objects in different directions. This technique involves a lot of math, since you also need to calculate the inclinations for the date and time you take the reading. The absolutely simplest and crudest form of navigating "by the stars" is having a stick that you hold out against north. As long as the ends of the stick is at the horizon and the north star, you are on the same latitude. If the star is below the end of the stick (when the other end is at the horizon), you need to go north, if it's too high, you need to go south. This is like the grandgrandfather of the sextant Then when you have a fix, you would use dead reckoning. I.e. you keep track of the time you go in a certain direction, and at what speed. Then you can draw a line on the chart for the direction, and make markings for distance traveled. When you turn, you make a new line, and so forth. You need to know your own position to be able to determine the (absolute) position of another ship. The relative position can always be found of course. To get the position for another ship using the sonar, you would start off by getting his direction by taking three bearings from the sonar at constant interval. Edit: You need to be stationary. (well, actually you don't, but then it get's yet a little bit more advanced.) This will give you the targets course, but not speed nor position. Then you would extrapolate, i.e. add another interval and draw a fourth bearing line. This line is where the target ship will be on at a specific time. But before that, you move your ship, so when it passes the fourth line you take yet another bearing reading from the sonar and draw a line. The target ship will be where that line intersect the "extrapolated" line. Once you know where it is, you also know where it's been (the other three lines) and where, so calculating the speed won't be much of an issue there. I won't get any deeper in this technique, since there's already great tutorials on the forums(fora) covering that. Using active sonar, you'd just take target ships bearing and distance, no fuzz. With scope same thing, bearing and distance (using stadimeter). Or time how long it takes the ship to pass the line in the scope, if you know the length of the ship. But it's still the same principle, distance over time. And then of course, you need to do it twice to get two different positions. Then just calculate the speed as distance divided by time. Last edited by Walle; 01-11-11 at 02:22 PM.

01-11-11, 11:17 AM	#2
Walle Watch Join Date: Aug 2009 Posts: 26 Downloads: 7 Uploads: 0	I like the 3 minute rule, or actually the 3:15 rule (more accurate). Make a mark on your target ships position and immediately start the chronometer (if you're zoomed in close and want precision, make the mark a little ahead of the ships stern or bow and start the chrono when the ship passes the mark). Wait 3 minutes and 15 seconds, and make a new mark (but don't stop the chrono). Measure the distance (i prefer the compass rather than the ruler). Now, the speed in knots is the distance in km multiplied by 10. I.e, the ship moved 1450 meter, then the speed is 14.5 knots. Since you didn't stop the chrono at 3:15, make another mark at 6:30 and multiply the distance by 5 to get an even more accurate reading. If you're using imperial instead of metric units, just multiply by ten and add a tenth, since a yard is roughly 0.9 meters.

01-11-11, 01:07 PM	#5
GertFroebe_neu Mate Join Date: Jan 2010 Location: Hamburg Germany Posts: 53 Downloads: 23 Uploads: 0	Hello! Thanks! Your postings were very helpful. Actually I thought there might be a gamefunction that would help with this, but I don't mind some calculating. How did the german uboat-commanders guess the speed? They did not have a selfupdating map ? cheers Marc

01-12-11, 04:14 AM	#12
Matador.es Chief Join Date: Feb 2010 Posts: 327 Downloads: 30 Uploads: 0	simple, get the ships lengt, measure the seconds it takes to move from the front to back over the vertical line of your scope. Divide meter by seconds, multiply by, 1.856 and you have speed in knots.