How it happens is explained by a plaque on the wall: digitized sounds of different instruments are associated with an invisible grid on three walls.

He was following, Jan knew, the invisible grid of sound waves created by beacons along the ocean floor.

The others are neatly folded, as if on an invisible grid, on long, low shelves.

That, plus the invisible grid inside her head, told her she had come to the edge of the humans' valley.

Each level takes place on a playfield divided into an invisible grid, each space of which can contain one object.

Could it be said, for example, that space is like an invisible three-dimensional grid in which the apple is positioned?

Would space as an "invisible grid" still exist?

Rhodan leaned far out over the balustrade until he was gently held back by the invisible grid of the energy screen.

I've counted footsteps and yards; I've even tried laying invisible grids over city maps.

Ms. Whelan travels along an invisible grid, twisting and pushing her arms and legs.