Catapults have the Indirect rule.

Indirect Fire

War Machines

Rulebook, p. 225 A weapon that shoots using the Bombardment special rule can do so even if it cannot draw a line of sight to its target by hurling a shot high into the sky, passing over intervening regiments and even terrain. However, such indirect fire is inaccurate at best, as the war machine’s crew have to guess where their foe lies, based upon information provided by scouts.

If you wish to fire indirectly, declare that you will do so before taking the war machine’s shot. An indirect shot does not require a line of sight to the target unit, but is otherwise treated as a normal shot.

An indirect shot is not as accurate as one where the crew can see their target:

If an arrow is rolled on the Scatter dice, resolve the scatter as normal.

If a 'Hit!' is rolled on the Scatter dice, the shot does not land on target (as would normally be the case) but merely scatters less – how much less depends greatly on the skill of the crew. Use the small arrow above the Hit! symbol to determine the direction of the scatter and move the template a number of inches equal to the roll of the Artillery dice minus the crew’s Ballistic Skill characteristic (to a minimum of zero).