Okay, rather than explain how to shoot a backsight (which you won't understand) I will instead explain what the Germans did in WWII.
If the Germans came upon a target that they wanted to shell but there were some structures that they needed intact, then they would recon the area and draw up a map. Then they would lay out the map with coordinate grids so that they might use math (geometry basically) to determine ranges. Then all they needed was one shot on any object in the target area, and then they would know the range to every other target (and bearing for that matter).
In Aces High we have the added benefit of the game telling you any time you destroy an object precisely which object it is that you have destroyed.
Now, as to the survey bit: When you are surveying a piece of property you use a piece of equipment called a theodolite. Today they have instruments that read GPS data, and can even map out structures by shooting millions of laser points and even determine color, but when it comes right down to it the instrument is determining bearing, and elevation. So, you take this instrument into the field and you locate known survey monuments. A monument can be a concrete marker, a nail in a road, or a steel rod in the ground. This is what a surveyor will 'tie' to when he establishes your property lines. That monument will be tied to a second monument just to establish a baseline. Once this is accomplished they will shoot a bearing a given distance according to the property description recorded at your local courthouse. Your property may have only three lines according to description, or many more, just depending on how the property line has been legally defined, but in the end the geometric lines of your property will return to the point of beginning. Then the surveyor can use math to determine if the geometric shape 'closes,' which basically means the total variation of distance around your property (geometrically) is zero (ends up where it began).
So, that's a lot of information that doesn't really help you, right? Well, here is where it does.
Once you have established the distance to a known object on your target then you try to hit the objects on the edge of the field (left and right) in order to determine the offset for your current position on the map. Once you have two known distances to objects on the field you can use Trigonometry to calculate the distance of every known object, or you can go with an estimate (experience makes a difference here). High Explosive rounds give a lot of leeway with this (up to 200 yds but at 200 yds it takes many, many more shots). You really want to get within 50 yds, and with experience you will.
Okay, so you have read a lot of stuff and you still don't know what to do. Well, this last bit I will not be precise on, because if you don't already know this about your tank then you don't deserve to know it. So, if you figure it out please don't pass it on or everyone will be shelling fields from 10k.
When you use indirect fire you do not use your gun sight. Shocking. I know.
So, in order to make this work you will have to find a way to shoot from the Commanders position that uses fixed objects to aim with while using something that will allow you to preset windage and elevation, because there are times when your center reticle will be way, WAY above the horizon. Offset windage comes in handy because there are times when you are not on level ground.
Whiskey, you should be able to figure this out without any more help.
And NO, everything you need is in the game already, so you do not need anything fancy to make this work.
