Model: a description or analogy used to help visualize something that cannot be directly observed.

That may be your personal definition, but is not the definition of that word in any context. Specifically, when discussing this topic - model means scientific model.

In any case, no models are used for sailing/traveling of any kind; your personal definition included.

Consult a dictionary

Practice what you preach! A flag is not a model either. Even if it were, you said it was "my model" which is also wrong.

So that's a horizontal drop of about 4 inches from the horizon that they have to account for.

Talk to an actual sniper. You are repeating nonsense. No sniper accounts, or needs to account, for any such thing. Even if such curvature existed, they don't need to adjust for it because they are never shooting blindly at targets hidden behind the horizon - that would be silly. Beyond that, other factors would be orders of magnitude more influential - like wind...

Model: a description or analogy used to help visualize something that cannot be directly observed.

That may be your personal definition, but is not the definition of that word in any context. Specifically, when discussing this topic - model means scientific model.

In any case, no models are used for sailing/traveling of any kind; your personal definition included.

Consult a dictionary

Practice what you preach! A flag is not a model either. Even if it were, you said it was "my model" which is also wrong.

So that's a horizontal drop of about 4 inches from the horizon that they have to account for.

Talk to an actual sniper, you are repeating nonsense. No sniper accounts, or needs to account, for any such thing. Even if such curvature existed, they don't need to adjust for it because they are never shooting blindly at targets hidden behind the horizon - that would be silly. Beyond that, other factors would be orders of magnitude more influential - like wind...