Thank you Fubar512, a tutorial like this is what i was looking for!
And FastCargo thaks too, good explanation!
My problem is that i am a beginer (i've been playing for 3 days), and i'm playing in hard (every seting in the game: radar, visual location, physics) and i am lost! I have to use the map in order to find the enemys (and discover their trayectory) because when I contact to the radio they told me the distance and the position of the targets only. And then, I never found them (sometimes, they are higher than me) and I think is very hard finding their tail so as to launch a missile (radar/heat coming). I think i've a lot of things to learn!
Anyway, thanks both of you for awnsering my questions!