Re: Introducing "Shooter", ballistics for Android!
Well I finally quit my smartphone (actually it quit me) and got an android. It's so much better than the WM, there's just no comparison.
The ease with which I've been able to do things with it is just scary including linking the blue-tooth to my truck, playing music, and downloading this awesome program. It's hard to believe it's free. As other have commented, I'd have been happy to pay for it.
Here are some observations from a fellow ballistics programmer:
1) The first thing I always do with a new program is input a known set of inputs and see if the output matches that of established/trusted programs. This one is very close, but I notice that it's a little fast (meaning more retained velocity at range and less drop). It's only a couple inches at 1000 yards, but it does make me curious about the solver and atmospherics. What solution method did you use?
2) Atmospherics is a separate question. Did you use the ASM or ICAO model? I hope you used ICAO, because it's a more updated model, and it's what most bullet companies correct their BC's for. Only Barnes Hornady and Sierra still use ASM, everyone else (Berger, Lapua, Nosler, Norma, Ruag and RWS) uses ICAO. There's about a ~1.7% difference in the standard air density between these two models. Mismatching the atmosphere effectively causes a 1.7% error in BC. Since your fields default to 29.53 inHg and 78% humidity when there's no GPS signal, I assume you're using ASM. I suggest including an option to select which standard atmosphere model is used so that users can match it to the atmosphere which the BC is corrected for.
3) The program is 100% adequate for solutions up to 1000 yards, which is beyond where most shooters 'max-out' practically. However, there are some additional ballistic effects you can provide the option to account for like spin drift (will require bullet length and spin rate/direction in addition to inputs that already exist) and coriolis effect (will require latitude and azimuth. Latitude can be obtained from the GPS, but I don't think the phone can find direction, can it?)
Adding the option to account for those 'second order' effects, and addressing the atmosphere/BC match will greatly improve the programs capability past 1k. <span style="text-decoration: underline">Good news is the math for these effects is relatively easy.</span> The formulas for coriolis and spin drift (it's just an approximation Lindy
) are published in
my book.
4) I would like to see a 'correction factor' to account for the fact that sight adjustments aren't perfect on all scopes. For example, if I move my scope 30 MOA, and the POI only moves 28.5 MOA or 32.4 MOA (errors like this are quite common) how do you use the 'pure' MOA solution? The correction factor would be a 'profile' variable.
5) Regarding the debate about weather to include 'sight-in' conditions... It's a good policy to work from a 100 yard zero. If you do that, I don't think you need to identify or account for the sight in conditions. There will be those who don't understand this and work from 600 yard zero's or something like that. For them it is necessary to know the sight-in conditions because the bullet travels thru so much atmosphere to get to it's zero range, and the atmosphere would affect the zero significantly. I guess this is a policy decision. If you want to enable shooters to do it the hard way, then you can add the capability. Personally, I would just encourage shooters to work from a 100 yard zero.
6) One more suggestion. I notice you don't have a bullet library. If you do consider adding a bullet library containing caliber, weight, BC and length (for a possible spin drift capability), I'll extend the same offer to you as I have extended to Brad (JBM) and the developer of the popular BulletFlight app for the iPhone. You can use my measured BC's in a bullet library. The values are very accurate and are referenced to the G7 standard (where appropriate). The inclusion of my measured BC's in both of the above mentioned programs is considered by their developers and users to be an important asset to the programs accuracy as opposed to using manufacturers advertised BC's. You can read some of Brad's (developer of JBM) comments about BC
here. All I ask is that you do not make the numeric BC's visible to the user. The reason is because those BC's are a great part of the value of my book and if someone is able to get them all in a free app, I'm frankly worried they'll be less inclined to buy the book! If you are interested in incorporating my BC's into a bullet library, and/or adding coriolis and spin drift effects, I'll be happy to donate a copy of my book for your use.
The above are my thoughts on possible improvements, but that's not to say the program isn't terrific 'as-is'. The interface is attractive an intuitive. The whole think is very well thought out and organized (thanks in part to the suggestions of some on this thread).
Thank you for offering this program and being so engaged with it's users on the development.
Best,
-Bryan
