Forerunner Slipspace 3

“I can see it, Doctor.” He ducked under the fuselage of a large satin-gray ship about the size of a Pelican, but he couldn’t tell if it was brand-new or if it had seen a thousand years’ service. He followed the sound of Halsey’s voice and stuck his head inside the first hatch he found open. “Is it just fantastically interesting, or is it actually going to be any use to us?”
Halsey’s indignant face popped up right in front of him, almost making him flinch.
“Yes, just a little,” she said. “You want to transform slipspace navigation? You want to know when you slip exactly where and when you’re going to drop back into realspace, and not end up hours and millions of kilometers from your target? Well, it comes as standard on every damn model in this showroom. And we’re going to have it.”
(Halo:Glasslands; Ch.12)

This explained how the Covenant could make jumps with such accuracy. They could literally plot a course with an error no larger than an atom's diameter.
(Halo:First Strike; pg.86)