Page "Line of sight (gaming)" Paragraph 3

A tank behind a tall hill would not be able to see an enemy tank on the other side of the hill.

Therefore, the first tank does not have a " line of sight " to the enemy tank.

Conversely, a squad of soldiers atop the hill may be able to see both tanks, though the tanks may not be able to see them ( since the tank's upward line of sight is limited ).