For some reason this reminds me of the video games that taught me to aim RPGs with iron sights by memorizing the dimensions of in game vehicles and comparing it to a little measure on the sight to estimate distance and so how far to adjust the aim upwards..
Information regarding what common objects your front sight is the width of at various ranges is pretty a standard inclusion (though not a particularly emphasized part) training in professional armies.
Many optical sights also incorporate similar features.
