help: range finding using scales

[ichso]

Hi there. I'm still quite new to SH4 yet, have played SH1 and SH3 very much in the past. I'm currently using SH4 1.5 with RFB 1.52. I have some slight trouble estimating the target range.
For testing I played a training mission with one ship standing still at ~1000 yards and another one at ~2100 yards. Identification gives me that both are some modern passenger liner ships with 120ft. mast height.
Using the stadimeter says that the closer one is ~1100 yards away. But when I want to use the TBT/Peri-Scales I get results that are a few 100 yards off.

For example: Att.Peri zoomed in, 7 small marks means (as I read from the manual) 1,75°. Then: target range is supposed to be:
range = mast height / sinus(1,75°) = 120 ft. / ~0,03 = ~3929 ft. = ~1300 yards. (At least the range dial says that it is supposed to be yards not NM). The difference between the stadimeter results and mine gets even bigger for the ship which is farther away (there it is ~2100 vs ~2800).

EDIT: after reviewing simple trigonemtry, I think this formula (from SH3 manual) is a bit too simple, you would calculate the hypotenus with it, not the needed adjacent. But doing it more complicated and correctly gives only a slightly better result and the problem remains.

Is this a result of unreliable information in the recognition manual or are the peri scales off ? I got similiar results when using the TBT. Also, it would be nice to enter the range manually without the ship being recognized as identified by the game (the yellow description in the PK console).

[CapnScurvy]

Is this a result of unreliable information in the recognition manual or are the peri scales off ?

BOTH.

You mentioned your using the RFB 1.52 mod. I should warn you that the optics for the periscope are not stock SH4. Some of the visual modifications that RFB has thrown in have changed the "AngularAngle" parameter of the scopes. Basically the view is magnified greater than the stock view. I wouldn't count on the periscopes hash marks being accurate (if they every were at all).

To check correct range of your two targets, either use the Sonar to ping an accurate range (make sure you "send" it to the TDC, the message log range estimate is just that an estimate. You'll get a true accurate range in the Position Keeper after you send it.) or set you options to disable (uncheck mark) the Manual Targeting System.

You may wish to look over this "post (http://www.subsim.com/radioroom/showthread.php?t=126016)" regarding Stadimeter range finding and why a ship sitting stationary at a known distance may give errors in manually found range. Drill down to the "Discussion" section to get an idea of what's what. I'm almost ready to release a version of SCAF for RFB 1.5 which will include the RSRDC v420 ships. You may wonder why are there different SCAF editions to be compatible with different mods. Some folks like to play around with different displacement values and the ships they do change sit differently in the water, which makes my task a bit more difficult to test each ship for each mod that's released.