Hi
Sounds like you are looking for something similar to a radar system. If yes, then you should check out this project:
http://www.engineersgarage.com/contribution/arduino-based-ultrasonic-radar
Although such ultrasonic sensors(used in above project) have limited range but it can be replaced with something that measures upto 300m.
I think you will have to look out for some industrial strength type sensors for the same.