Search found 882 matches

by Bill Jurens
Fri Oct 13, 2006 2:43 am
Forum: Naval Technology
Topic: Iowa Class real performance
Replies: 67
Views: 34361

Faceplate penetration

Well, you sure know how to flatter a guy... I am working on a number of other things now, but your kind comment enticed me to do a quick 'back of the envelope' calculation using the USN's official ORD SK78841 as a guide. This suggests that penetration of an Iowa faceplate by a 15" bullet was im...
by Bill Jurens
Thu Oct 12, 2006 6:19 pm
Forum: Naval History (1922-1945)
Topic: South Dakota´s barbette impact
Replies: 9
Views: 3087

Barbette impact

The hit on South Dakota is unlikely to have been from an armor-piercing round. The steel doesn't lie; an impact from an a.p. round would have caused much more damage at the impact point, and the amount of damaged and removed decking is much too large to have been removed by the relatively small char...
by Bill Jurens
Thu Oct 12, 2006 4:34 pm
Forum: Naval Technology
Topic: Iowa Class real performance
Replies: 67
Views: 34361

Armor impacts

The hit on South Dakota is unlikely to have been from an armor-piercing round. The steel doesn't lie; an impact from an a.p. round would have caused much more damage at the impact point, and the amount of damaged and removed decking is much too large to have been removed by the relatively small char...
by Bill Jurens
Mon Feb 27, 2006 4:58 am
Forum: Bismarck General Discussion
Topic: Determining Distances from Photographs
Replies: 57
Views: 27567

Photogrammetry

You can disagree all you like, but I'll stand by my statements, with a few comments. I will reiterate that the analysis of these photographs in many cases amounts to a Rorsach test. With apologies to Simon and Garfunkel, "... A man sees what he wants to see and disregards the rest..." You ...
by Bill Jurens
Fri Feb 24, 2006 5:59 am
Forum: Bismarck General Discussion
Topic: Determining Distances from Photographs
Replies: 57
Views: 27567

Off-the-wall

The photogrammetric equations are rock-solid and will give correct answers to any degree of precision one wishes. Unfortunately, accurate photogrammetric analysis requires the precise measurement of very small distances -- sometimes to within a couple of thousandths of a millimeter in size -- and th...
by Bill Jurens
Tue Feb 21, 2006 2:36 am
Forum: Bismarck General Discussion
Topic: Determining Distances from Photographs
Replies: 57
Views: 27567

Photogrammetry

For what it is worth my photogrammetric analysis of this photo strongly suggests that it was indeed taken with a 50mm lens on a 35mm camera. The general field of view of what appears to be a nearly full-frame reproduction closely matches what might be expected using a 50mm lens on 35mm film, and oth...
by Bill Jurens
Sun Feb 12, 2006 12:39 am
Forum: Bismarck General Discussion
Topic: Determining Distances from Photographs
Replies: 57
Views: 27567

Speed changes during maneuvering

I am not certain how well the new -- or for that matter the old -- track charts account for the speed losses typically experienced during turns, which can be quite considerable. The exact amount of the speed loss during turns varies quite a bit with sea state, and even varies from ship to ship of th...
by Bill Jurens
Sat Feb 11, 2006 7:48 pm
Forum: Bismarck General Discussion
Topic: Determining Distances from Photographs
Replies: 57
Views: 27567

Photogrammetry, etc.

My analysis of NH69722 used a variety of methods. One of these involved comparing the relative size of Bismarck to that of various and sundry foreground objects after resecting for camera position. This resection checked for a field of view equvalent to a 50mm lens, which is one reason I believe the...
by Bill Jurens
Fri Feb 10, 2006 3:35 am
Forum: Bismarck General Discussion
Topic: Determining Distances from Photographs
Replies: 57
Views: 27567

Photography

It is worth noting that when examining prints of poor quality photography -- which this certainly is -- it is generally impossible or at least very difficult to determine whether a change in image size is due to a change of lens or a change in enlargement made in the darkroom. My guess is that the c...
by Bill Jurens
Fri Feb 03, 2006 3:49 pm
Forum: Bismarck General Discussion
Topic: Who really sank the Hood? Bismarck or Prinz Eugen?
Replies: 45
Views: 87331

Forward Magazine Explosion

The documentary suggesting the forward magazine explosion, which is not too bad otherwise, keeps coming up again and again. As a member of the Marine Forensics Committee of the Society of Naval Architects and Marine Engineers, and the author of "The Loss of HMS Hood -- A Re-examination" I ...
by Bill Jurens
Thu Jan 26, 2006 6:33 am
Forum: Bismarck General Discussion
Topic: Determining Distances from Photographs
Replies: 57
Views: 27567

Photographs

Your initial hypothesis regarding photogrammetric calculations is incorrect. In fact there is no justification whatsoever to support your statement that that there are no equations that can be used to compute distances in front of the horizon. The geometry about the horizon line is (nearly) symmetri...
by Bill Jurens
Thu Aug 25, 2005 4:24 pm
Forum: Books and Reference
Topic: For young Mr Jurens!!
Replies: 4
Views: 2606

Old Warship Internationals

I did indeed receive the lists I was looking for from a gentleman name Art Mears, in eastern Canada, an ex-SeaBee. I haven't heard from him in years, but still appreciate his efforts. It's hard now to recall how long ago this was, both in terms of time passed, and in terms of how things are done now...
by Bill Jurens
Sat Aug 20, 2005 11:12 pm
Forum: Bismarck General Discussion
Topic: Photo # NH 69722 distance evaluation
Replies: 80
Views: 40535

Photogrammetry

I must begin by thanking Jose for issuing me a new password which allowed me to enter the forum again. I have been having difficulty logging on over the past few days. I have been following the thread regarding the analysis of Denmark Strait photography for several days now. With respect, I'd sugges...
by Bill Jurens
Wed Jul 13, 2005 10:55 pm
Forum: Naval Weapons
Topic: Hoods rangefinder (instrument)
Replies: 7
Views: 4194

Clocks...

You are probably referring to what was typically known as a 'range clock'. These items, which varied somewhat in appearance from navy to navy and from time to time, had a large (usually) circular clock-like dial facing fore-and-aft, with hands that could be moved to indicate (via a variety of system...
by Bill Jurens
Sat Jun 25, 2005 11:43 pm
Forum: Bismarck General Discussion
Topic: DS reversed photo theory and battle maps comparison
Replies: 63
Views: 35352

No Vendetta

Hello, Bob: No vendetta, honest. I was responding to your often-repeated statements that your theory was supported by various individuals and institutions, and more precisely to your implication that these endorsements, apparently dating back to 1993 or so, are still relevant. One very recent exampl...