speed estimation using scope/uzo reticule_finished

[greyrider]

There are a number of ways to determine target speed on the forums,

there's the stock tdc, wazoos method, the speed/rpm charts, and
maybe a few more that i dont know of.

This little tutorial will demonstrate how to use the periscope or
uzo reticle, with no auto-tdc, or no manual tdc either, in other
words, 100 percent realism, to determine speed.

This method is very easy, its one of three mini tutorials that i
want to put out, the other two will cover range estimation using the
optical devices,
the other being target course estimation using the optical devices.
.

All three of the tutorials will require you to observe the target, so
in order to use these methods, the target must be seen.

PERISCOPE VERTICAL STADIMETER SCALE

As you are well aware, the scope vertical scale can be used to determine target range,
but it can also be used to determine target speed.

To determine speed using the vertical scale, we are only interested in using the vertical line
as a start point and an end point, in which to measure the time an object takes to
pass threw the vertical line, from bow to stern.

You have to be as close to a 90 decree angle to target course as you can be, so that
you will be able to observe the total length of the target in order to get an accurate
speed estimation.

This can be used with wazoo's fast 90 method, but instead of trying
to match the speed of the target, stop the u-boat, become motionless, and then measure
target speed using the vertical reticle line of the optics.

RECOGNITION MANUAL

The ship recognition manual contains the length of all the ships in shIII measured in meters.

All we need to do to determine a targets speed is to identify the target ship, turn to the recognition
manual, turn to the page of the target we are observing, and read the targets length from the manual.
Then use the vertical scale to measure time, then one TSD calculation, and we have target speed.

DETERMINING TARGET SPEED

Below is a picture of a target heading 90 decrees relative to the u-boat, sonar will report the target
as long range, its range is 4 km and the target is a c-3 cargo ship.



Now that the target has been identified as a c-3 cargo ship, we turn to the ship recognition
Manual, and read the length of a c-3 cargo ship, which is 150 meters long.



But now, another target approaches, its another c-3 cargo ship, heading 270 decrees, relative to the u-boat. Its range is 1500 meters, and sonar would report its range as medium.



MEASURING TARGET SPEED

First step: line the bow of the target so that the bow of the target just touches the vertical line.
(see picture below)



Once the target’s bow touches the vertical line, click on the chronometer and time the time it
takes for the full length of the target vessel to pass the vertical line of the scope. Once the targets stern touches the vertical line of the scope, stop the chronometer, and read the time elapsed.





In this example, it took 42 seconds for the c-3 cargo ship to pass the vertical line, from bow to stern.

LONG RANGE TARGET

Going back to the long range c-3, we measure the speed of this ship, just like we did for
the medium range target.





The long range target also took only 42 seconds to pass the vertical line from bow to stern.


SPEED FORMULA

So now we have an object 150 meters long and that object took 42 seconds to pass our
reference point. We measured our time in seconds, but speed is measured in hours,
knots for example. We need to convert easily from seconds to hours so that the end result
for the speed calculation will give us the speed in knots per hour.

I use nauticalc plus, a calculator for sailing, boating, navigation. I just press buttons and I have
Solutions in seconds, its my electronic weapons and navigation officers onboard.

http://www.calculated.com/productcar...1&idproduct=32

But for this tutorial, we will use a math formula, to determine the target speed that we just measured.

Since we measured the length of the ships speed in seconds, we must convert one hour into seconds, so that all of the data is on the same sheet of music.

Sixty seconds times sixty minutes gives us thirty six hundred seconds in one hour.

60 * 60 = 3600

In place of one hour we will use 3600 seconds instead, since our measurement was in seconds.


So, the calculation starts out finding the distance an object 150 meters long would have traveled
In one hour;

3600 seconds X 150 meters length of ship = 540000 meters per hour.

The total distance is then divided by the time we observed the target pass threw our reference point, which was 43 seconds.

540000 meters per hour / 42 seconds = 12857 meters

12857 meters is the distance the target would cover at the speed its going, now we just have to convert meters into knots.

One nautical mile is 1852 meters, we need to divide 12857 meters by 1 nautical mile or 1852 meters to get target speed in knots.

12857 meters / 1852 meters = 6.9422 knots.

So both targets are traveling at 7 knots.

Now we have target speed and we didn’t use the tdc at all to get it, we just used the periscope
Itself.

MATH FORMULA

Its easier than I explained it:

This is the math formula to use for calculating target speed with a periscope or uzo reticule.

3600 x length of ship / observed time / 1852 meters

SONAR CHECK ON TARGET SPEED



AUTO TDC CHECK



END OF TUTORIAL

[Tonnage_Ace]

My hero! Great tutorial! Always hated that 3:15 method becuase the ruler is so innacurate(300m means 250m). The target's heading can be off by a couple degrees, but the speed is what makes all the difference, I'll be using this frequently!

[finchOU]

not to shoot down your method or anything...but if you already have solved for target Course.....you should have gotten Speed as well?......stopping the U-boat is not practical in combat and should not be possible in the sim without drifting (or if submerged broaching or sinking).....an easier method would be the fast 90. Interesting method none the less.

[greyrider]

finchou wrote

stopping the U-boat is not practical in combat and should not be possible in the sim without drifting

thats not exactly true finchow, you here and see the ai dd's stop, shut down all engines, drift and listen

and in real life, even the infantry takes many listening halts
in a movement to contact, or recon and combat patrols

and when the u-boats submerged, and its engines stop, it does drift for awhile, then inertia will take over and stop the boats drifting

in calm seas, i dont see any reason why the planesmen cannot keep the boat level

another thing subs had to maintain level where trim ballast, these were smaller tanks, that could let water out and air in to trim the boats depth in small increments, i never heard of subs having trouble staying at depth, unless they where very deep, and the water pressure pushed them deeper, but then i can only read so much.
sorry my answer is in the quote, i hit the wrong key,and i cant correct it now.

[Phylacista]

Looks great -

but does it only work when AoB is near 90?

e.g.: target is at 45°: when looking at it its not only shorter (in the scope) cause of the angle but the speed you measure is only hmm lets say "perpendicular speed" (hope you get my meaning).

If thats the cause you could only get speed with your method when the target already passed optimum shooting angle.

[Tonnage_Ace]

Originally Posted by greyrider

finchou wrote

another thing subs had to maintain level where trim ballast, these were smaller tanks, that could let water out and air in to trim the boats depth in small increments, i never heard of subs having trouble staying at depth, unless they where very deep, and the water pressure pushed them deeper, but then i can only read so much.
sorry my answer is in the quote, i hit the wrong key,and i cant correct it now.

I mentioned this earlier. If you set all stop in the 'red zone' you'll drift deeper but if your in the yellow, you'll stay at set depth so it shouldn't be a problem.

[Dantenoc]

Originally Posted by Phylacista

Looks great -

but does it only work when AoB is near 90?

e.g.: target is at 45°: when looking at it its not only shorter (in the scope) cause of the angle but the speed you measure is only hmm lets say "perpendicular speed" (hope you get my meaning).

If thats the cause you could only get speed with your method when the target already passed optimum shooting angle.

I think you're right... the method is very precise at 90 degrees AoB, but degrades significantly as the AoB increases or decreases. You could compensate using trigonometry and AoB though, but knowing the exact AoB of a target that's far away isn't that simple

Good tip, though, and something that can be built on

[greyrider]

there are other ways using the scope scales to get speed,we can also use the horizontal scale for speed estimation, and this way will demonstrated getting target range, plus speed, on a target heading right at you.

i have made some range charts for all the merchants in sh3

on scope and uzo magnifications of 1.5x, 6.0x, and 7.0x

for every ship, (merchant that is ) i computed the range
for the first 10 ticks marks of the vertical scale.

for instance, if your looking threw the scope at a target, lets say a c-3 cargo ship, and you measure from the waterline, to the top of the mast, and the target takes up the space of two tick marks of the vertical scale, at 6.0x for instance,then the range of the target
is 2979 meters.
so , by looking at the target threw the scope , we will get range to target by checking the charts.

ok, now to get speed from that, ok lets say you measured the range manualllay using the charts, and you recorded what i wrote above

2 ticks marks
c-3 cargo
time 10:00

ok so now your ovserving the target closing, you know range, but not speed. you want speed.

since we know that at 10:00, we ranged the target at a known range, 2979 meters at 2 tick marks, now we turn on the chronometer, and time the targets advance until the target fills three tick marks, another known distance, because at three tick marks, a c-3 cargo ships range is 1986 meters. and it took the c-3 2 minutes to get to the third tick mark.

now it becomes a TSD problem again.

minus the distance 2979 meters from 1986 meters, and the answer is 993 meters travelled in two minutes.

t = 2 MINUTES

d = 993 meters

we solve for speed = 16 knots

now we have range and speed of target, just using scope, no tdc.

you can also using the horizontal scales to for range and speed, only you are using the width of the beam, instead of mastheight
at any distance out to the extend of visual range