Manual Artillery Firing

[ninhydrinal 1]

So I've been practicing firing mobile artillery without the use of the artillery computer but I've hit a weird issue. No matter how many times I run the equation, the elevation is always off by +- 3 degrees. I've been trying to figure this out all night with very little to show for it. Does anyone know why this happens?

 

I'm using the worksheet from this video: https://www.youtube.com/watch?v=A4SPene9Yxw

And I'm also using this spreadsheet: https://docs.google.com/spreadsheets/d/1q4PWQ4b6azx7YAKrRErsdKEiaYvuJzp0Who7V0batAc/edit?pageId=116206726297015043606#gid=0

Here's an album showing my battery, target, and the line of sight targeting, which shows what the elevation should be: http://imgur.com/a/jYKZG

When I plug those numbers into the equation/spreadsheet I get this: https://i.imgur.com/1nnLnzu.png

 

The elevation that it tells me to range for in this case is a complete degree off. If I fire here, my rounds will be landing short of the target. In this particular instance my forward observer could tell me that and I could adjust accordingly. However on most targets that difference is up to 3 degrees off so when firing long distance, my rounds will be landing far away from my target and I end up hitting friendlies.

[x3kj 1247]

That is because this formula is not really correct - it's a handformula from somewhere else. Nowhere does it consider the drag of the Projectile (the stat is called airFriction in configs) - so if 2 different projectiles have different stats, you will end up with the same angle after this calculation, when in the game you would need different elevation to achieve the same range. (same is already written in the comments to the video you linked)

 

To receive fairly accurate solutions you would have to use an active calculator that integrates over time or in other words: simulates the gradual decrease of projectile velocity with the exact same formula that the game uses.

If you want some basic calculator you can google for DUST2DUST's Ballistic Calculator. It's fairly clunky and could be better executed in terms of usability/presentation. And it only calculates point of impact for given inputs, not the required elevation angle.

 

I have made an excel macro based on the same principle that can automatically calculate range tables for any range you desire, and the max range of the weapon to aid the development of weapons for my mod. I have to adjust it a bit to make it usable for other users/ vanilla content though - so it's not quite ready yet.  And i don't have informations about the long range accuracy of the results yet. If you wanna help in testing it you can send me a PM.

 

Edit: Actually i just checked configs, vanilla artillery do not have any airfriction (82mm Mortar 155mm Howitzer 230mm MLRS) o0

[x3kj 1247]

Here is my calculator spread sheet, as said, it is not yet ready for calculating via positional input or for calculating for targets at different altitude. But i plan to add that

https://forums.bistudio.com/topic/186984-x3kjs-ballistic-calculator-excel-macro-sheet/

[ninhydrinal 1]

Yeah, I thought the issue was going to be drag as well but it threw me off when I found out that the airFriction to the shells is 0. Something has to have changed since SMPCrafters released that video. I'm placing my scorcher in almost the exact same location but shooting at a different target. He was able to get an angle that was only 0.19 off so the equation did work when he posted it.

 

The formula is also a well known one for projectiles. https://en.wikipedia.org/wiki/Trajectory_of_a_projectile#Angle_required_to_hit_coordinate_.28x.2Cy.29

 

I'm taking a look at your spreadsheet and it still seems to be off. I placed 2 scorchers apart from each other on the salt flats, both at 3 elevation, just 1280m apart. The in game artillery elevation control tells me I should be aiming at 72.47 but when I plug the range into your sheet, it says to be aiming at 73.99. Something still seems to be off.

[x3kj 1247]

At that short range and the high angle the actual error - meters of impact off target -  neglegible and more governed by artillery dispersion.

 

I tested my solution on altis with a target at same heigth @ 2050 @ 4750  @ 11700 and @15500 m compared to what the artillery computer gives you (if you just click on the map in artillery computer, it automatically elevates the gun to the angle of the solution).

@ 4750m  computer: 64.0 charge 2 ;   mine: 64.09 charge 2

@ 11700 computer 65.14 charge 3;  mine: 65.225 charge 3

@ 15500 computer 79.3 charge 4; mine: 79.418

 

Only at 15500 the rounds landed a bit short, but this may also be due to with charge 4 and almost maximum elevation, leading 2min traveltime and therefore huge spread. I have only fired 5-6 rounds for this range. With direct fire the rounds where a bit too far (something like 200m at 15km), which i suspect is due to the heigth of the gun - at those flat angles, and additional heigth of 2m can mean quite a bit more range. Additionally, if the vehicle does not stand on perfectly flat ground, the solutions will be off by the amount your vehicle stands angled... the artillery computer and the visual targeting thing seem to compensate for this.

 

You need a spotter for targets you have no line of sight to anyway though

[ninhydrinal 1]

I'm not at home right now so I can't do any further tests but I will be when I get back.

It's not negligible at short ranges. In my scenario, being off by more than 200 meters can result in friendlies being shelled. In short ranges, that I've zeroed in on, the dispersion hasn't been more than 100 meters which is fine on target. I've done tests from 1.2km to just over 9km, while on flat land, and it's consistently off by +- 3. I'll expand on this later with more images/math when I can. I am using a spotter but this should still be able to get me on a 100 by 100 meter gridsquare with the first round.

 

Edit:

Here's what I mean. I took the same target, at 3 elevation, and ranged it from similar areas but at a slightly different elevation. 

 

Same Elevation: http://imgur.com/a/RF9E8

 

+11 Elevation: http://imgur.com/a/CDpnd

 

This is eye opening to me because once I raise my elevation by 11, my artillery elevation is thrown off by 1.68 degrees.

 

Edit 2:

So I did this test again at an elevation 90m, aiming at the same target, and my artillery elevation is off by  1.74 degrees this time. Such a huge difference in elevation but it didn't throw it off much further than when I was only 10m higher than the target.

[x3kj 1247]

you are calculating with g= 9.806 that is wrong. gravity constant is 9.81 ingame.

[ninhydrinal 1]

Changing it from 9.80665 to 9.81 only changes the angle by 0.02 at 13.5km.

[x3kj 1247]

elevation deviation doesnt matter. At all. what matters is the impact location.

[ninhydrinal 1]

You're missing the problem completely here. When the altitude difference is 0, I'm on target. The second I go up by 11 altitude, I'm off target by almost 2 degrees. That would mean that in the equation, something with y is causing that deviation. I have no clue why though and that's what I'm trying to figure out.

[sketchh 11]

NINHYDRINAL, check out my post.  I'm not sure what the issue was with your calcs, I didn't look. Hoping this helps.

 

https://forums.bistudio.com/topic/187992-ballistic-computer-artillery/

[NoBodie 0]

Trying to get that newbie forums checked off so I can start a new thread.  Read almost all Arty related post i could find.

 

I'm trying to get an artillery battery to fire on a support request. I have 6 units (same type) grouped sync to a arty support provider which in turn is linked to a support requested and in turn sync to the player. Every time I call for fire only 1 gun fires. How do I get all six to fire?

Pics below of setup.

http://s1356.photobucket.com/user/NoBodie1/slideshow/ARMA%203