You don't need to reinstall the game.
Just have to press this button:
These are the steps to follow:
- make sure the Position Keeper is OFF since it changes the TDC data using the speed determined for the previous ship you attacked. So PK is OFF.
- Estimating the speed is affected by the efficiency of the crew, so it is useful to be in "battle stations" mode.
- identify the ship so the correct mast height is set in the dial.
- lock on the target. if the target is not locked the bearing will be off by at least one degree and you may get speed estimates in the range of 50 knots.
- do a range measurement with the stadimeter and send it to the tdc
- lower the periscope to avoid being seen
- wait for 10 seconds (any more than that is useless)
- raise the periscope
- lock on the target. if the target is not locked the bearing will be off by at least one degree and you may get speed estimates in the range of 50 knots.
- do a range measurement with the stadimeter and send it to the tdc
- press the "Estimate target's speed". The estimated speed is set inside the dial (and typed in the message log). Pressing the button many times will produce different values, because of the human error. It is wise to send to the TDC the average of the given values.
- send the speed to TDC
- determine AOB
- now the data are correct and you can activate the PK, lower the periscope and attack completely undetected

So this not quite "automatically", but at least you have the firing squad to do all the math for you:
- pin-point the positions (measured in degrees of latitude and longitude) of the target on the map (with almost GPS precision) based on the relative position of a target to the (moving) position of the sub. The parameters are the distance and the relative bearing to the target and the heading of the sub.
- measure the distance between the 2 positions (this is in meters or yards)
- determine the speed, knowing the distance and the time (this is meters or yards per second)
- transform the speed in knots (based on the average length of the nautical mile).
So, I guess that this math was what ticked everybody off when they said the stopwatch was broken

. Basically, the stopwatch was only meant to give you the time between the range (and bearing) measurements. You had to do everything else, flowlessly, fast, every time

. Well, no more!
PS: the system works even if there is no target in a thousand miles. So the system actually does all that calculations. Is not based on the fact that the game knows the position of all ships in the mission. You can do measurements of range and bearing "in clean air" and ask for a speed estimate with no problem. That's why is critical to lock on the target, so the result is the speed of that particular ship.
PPS: when you raise your periscope for the second range measurement, make sure you lock on the same ship. If you don't, the system will think the ship has teleported and report very high speeds

. So when you see incredible speed estimates, it means you missed the ship and locked on another ship of the same class that's after you.