Re: Introducing "Shooter", ballistics for Android!
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Lindy</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">1) Not all the programs are using the same equations to compute the Air Density Ratio. Many programs are just based on simple models and simplifications. Granted, a good number of users won’t see the difference, but at LR it really matters.
2) Those “trivial” equations are really driving a lot of errors. The exact equations and model are far from being “trivial”</div></div>
Well, they are probably not trivial to most shooters - but I'll guarantee you that they're trivial to the people who write the software. There is no mystery or magic about draq equations.
In any case, I'm not arguing for, nor do I use, ballistics programs based upon simplified models.
This discussion is about the importance, if any, of being able to enter environmental parameters as density altitude, about which all you can say is,
<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">Having a single parameter to deal with, is obviously a more simple way than to deal with 3 or 4. Simple probability indicates less possibility of input error.</div></div>
This is simply an attempt at
Proof by Repeated Assertion. Apparently you are willing to believe that people who are making long-distance shots with complex weapon systems are unable to correctly enter three parameters into a ballistic program, rather than one.
Personally, I have far more respect for the people we train in the art of shooting long distances than you do. Of course, I'm not trying to sell anyone on a particular ballistic program, which you appear to be.
<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">The difference of Sight-In conditions versus the actual Field Conditions is always there. A short ZR of say 100 yards, with a change of Air Pressure of just 2.0 inches and a slight temperature rise of 6 deg F will make a change in POI of 2.0 MOA at 1000 yards, creating a “parallel path curve”</div></div>
I'm afraid that turns out not to be the case. The POI on a thousand yard shot will in fact change by roughly that amount with that magnitude of change, but it's not because of a change in the short range zero. It's because of the difference in air density. All ballistic programs take that change into account.
Change in zero conditions matters for all practical purposes only when using extended-range zeros. If you're shooting a Barrett M82A1 with a 60 MOA base on it with a scope zeroed at 1000 yards, then yeah, you better take a change in zero-range conditions into account. That's not the case with a 100 yard zero.
In any case, both of the ballistic programs I use in the field allow for recording the air-data conditions for the zero range, and compensating for changes in them, at ranges where that might be useful.
My point in this discussion was that there is no need to use density altitude in a field ballistic program. Irrespective of the merits of any particular ballistic program, you have completely failed at trying to establish a need for that, except to avoid user input errors on three numbers rather than one.
I do not find that argument compelling, alas.
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1) With all due respect, it seems to me you are not doing your homework.
2) The POI shift is caused by not accounting the difference in Sight-In versus Field Conditions. As simple as that…you can forever trying to say the other way around, but it’s there you like it or not. And to prove that just do some basic math.
3) That effect is very well known as “parallel path curve” for any serious ballistician. The net result if a shift of the TRUE Zero Range, as it wanders along the LOS line.
4) In Exterior Ballistics, that effect is perfectly explained by the principle of the “Envelope of Trajectories”, also take a look to the “Non-rigidity of trajectories”
5) If you don’t account for that, your program will yield two curves with the same ZR, which is WRONG. I mean when comparing a trajectory based on Sight-In conditions versus another one based on current Field Conditions.
6) Not trying to repeat myself, but it’s simple probability calculus that the stochastic probability of the input error of 1 parameter is about 85% less than when dealing with 3 or 4 parameters.
7) If you don’t like the use of DA on a mobile device, well, that’s your privilege. Others tend to think different.
8) Of course we can use (and I do) 3 or 4 parameters, that’s what not the point of the original post at all. Please do not deviate the subject.
9) The whole point is discussing LR situations, where a savvy shooter will try to account, as much as possible, for every possible source of error.
10) BTW, I’m not trying to establish nothing, as is your case, just sharing my thoughts and mathematical facts.
It's nice and round as of v2.0. 
