Hello All ;
To Mr. Gardner:
I thought we went over this once before. OK, let's try it again ( I will be quoting myself, as apparently you didn't read it the first time.) The equation :
E = (58.2R^2)/BM Where:
E = the error in range in yards
R = range to target in yards
B = base length in yards
M = magnifying power of the instrument.
a calculation of the intrinsic error of a rangefinder, rather it is the equation for determining the amount of what was called a 'Unit of Error". or the amount of error created by a 12 second arc error in the range determination.
This is important, as this is what was used to determine if it was necessary to do a correction of the optical system using the soft wedges. By careful adjustment, it was possible to correct that range finding system so that at 10,000 yards, the read error was within 20 yards of the true range.
In addition, by careful training, and using techniques such as only approaching the range reading from one direction to eliminate the hysteresis ( or backlash ) of the adjusting unit, skilled operators with experience and exceptional eyesight could get VERY accurate readings, even at long ranges.
You can read all about the Mk58 optical rangefinder at
As for the Mk8, According to the Manual, which you can read at
The minimum distance between gradations on the CRT screen was the equivalent to 200 yards, and, what is further of importance, that the stated maximum range accuracy was +/- 15 yards + 0.1% of the measured range. Thus, at 10,000 yards, the maximum error was as much as +/- 25 yards.
However, to this must be added a caveat: The 'pip' that was being measured manually on the screen was between 15 and 18 mils in width, and, with the flickering of the system, could introduce an additional error of as much as +/- 50 yards, and this was independant of range. Thus, at 10,000 yards, the error in range as read on the Mk8 at 10,000 yards could be as much as +/- 75 yards, or 150 yards total.
Which brings us to another point. The calibration of the Mk8 Radar itself. WW2 radar relied on Cavity Magnetrons, which, being made under wartime conditions, were shipped with only the most rudimentry calibration by the factory. It was required, when they were installed, that they be calibrated in the radar system itself. This was done on board ship, and, interestingly enough, when it came time to do the range calibration, the technique was to point the mount, which had both the optical and radar range units mounted to it, and, using a distant ship as a target, use the optical system to supply the range figure to which the radar was calibrated to.
In effect, the radar could NEVER be more accurate than the optical system, because it was calibrated from it.
Finally, a good summary of some of the issues afflicting USN wartime radars are mentioned in the following article, ' Automation's Finest Hour: Radar and System Integration in World War II ' , by David A. Mindell, which you can find at
To Mr. M. Falcon :
Probably poking the bear but humans were not even around 600 million years ago. Even red herrings hadn't evolved by then.
We didn't evolve radar but that doesn't make it inferior to vision. For example no sane pilot would attempt to land an aircraft in fog at night by Mk1 eyeball alone if radar was available.
According to the latest theories relating to evolution on our planet, the first micro organisms with what are believed to be a visual receptor that we could describe as a predecessor to the eye developed approximately 550 million years ago. I don't know about you, but I can trace my family tree all the back to that time .....
As for landing aircraft, Mr. Falcon, exactly HOW MANY aircraft have you personally landed ? In
ANY weather ? Me ? A lot. Of different types, under a lot of conditions. And here is a kicker for you. When you are landing on IFR, at night, in fog, you ARE NOT landing with radar. There is a radar operator on the ground that may be watching you crash, but when you are on short final, you are using the Mk 1 Eyeball to pick up the runway lights and the threshold so you can land.
Which brings us to another point: Which would you think is more accurate for a landing in CAVU conditions: A pair of eyeballs or a radar? Let me give you a hint: Its the ones that can blink, and distinguish different colors. Something radars can't do yet.
And now I am going to tee off on several of the posters in this thread: You insist on pitting the Iowa of 1944 against the Bismarck of 1941. This is like pitting a 1944 P-51D against a 1941 P-51A. Not much of a contest.
I propose a different matchup: Let us pit the Bismarck of 1941 against the USS Iowa of 1941. OOOH - Wait ! HMMMMMMMMM..... That's not gonna work, is it....
OK - Instead, let's pit the Bismarck of 1941 against the USS Washington of 1941. That's right. Let's see if the Showboat, with her vibrating turbines and prop shafts that mess up the fire control at any speed over about 25 knots could go up against the Kriegsmarine's finest.
If we compare apples to apples, we find that the applesauce is considerably different.
Paul R. Ward