UPEMB%SEGUC11@gd3090.gd.chalmers.se (Mikael Borgman) (04/19/91)
From: Mikael Borgman <UPEMB%SEGUC11@gd3090.gd.chalmers.se> Just a thougth concerning the elevation of guns, howitzers and such. How do you measure elevation? The angle between the barrel and the ground, or the angle between the barrel and a straight line from the gun to the target. >From: thos@suite.sw.oz.au (Thomas Cohen) >Although AA guns are allowed to fire over 45deg I believe ;^) It seems that if you define elevation in the second way a AA-gun would fire with elevations of less than 45 deg, thus it is defined as a gun. (I could imagine a AA-howitzer firing at angels above 45 deg and hitting an aircraft from above, but you'll need a hell of a fire control system :-) Mikael Borgman upemb%seguc11 at gd3090.gd.chalmers.se
emery@aries.mitre.org (David Emery) (04/24/91)
From: emery@aries.mitre.org (David Emery) Elevation is the angle from horizontal (measured by a level) to (a line running through the center of) the barrel. This is true for both Field and Air Defense Artillery, I believe. In general, angles in artillery are measured in "mils". A "mil" is the angle subtended by 1 meter at 1000 meters. (There are about 17 mils per degree, and 6400 mils in a circle). What happens when the target and the gun are at different heights? How is that "angle" handled? This is a bit hard to explain without a picture, but let's try an example. Assume that the target is 4km away, and it is 20 meters above the gun. The angle between a horizontal line and a line from the gun to the target is called "site" (I don't know why it's called that...). In my example, this angle is 5 mils (20 meters/4km). (Now you understand why we use "mils" to measure angles.) This value is added to the elevation needed to reach a target 4 km away, yielding the "quadrant setting" which is actually set on the guns. (Actually, it's a bit more complicated as you have to compensate for some differences in trajectory, not to mention stuff like air pressure, powder temperature and actual muzzle velocity...) When doing manual gunnery, you have some "slide rules" that calculate this "site angle" and the elevation needed to hit a certain range. There are some inaccuracies, particularly as you approach minimum or maximum ranges, but if you're careful it's accurate enough. Automated gunnery takes a different approach. It "shoots the bullet" at some initial elevation, calculates the impct of the bullet at that elevation, and then determines the difference between the target and the "did hit" location. It estimates the change needed to move the bullet to the target, and iterates until the "did hit" location is the same as the target. dave emery