Sprinkler Daddy Says:
Head to Head Coverage = Happy Grass

Head to Head Coverage Explained

Head to head coverage is the manufacturer's recommended way to design sprinkler systems.  Basically, the further along the spray you go, the less amount of water that covers the ground.  So if you just sprayed so that you got all the grass wet, you'd have to over water in some areas just to get the bare minimum on the other parts.

So essentially, head to head coverage means that you'll install a few more heads up front, but you'll save water and money every time you water your lawn.