GPS lines: Abbr.

RDS

Think of the three-letter abbreviation for the network of numbered routes that help drivers navigate, often marked on maps with shields.

GPS lines" hints at the roads or routes a GPS system uses to guide you. The abbreviation "RDS" stands for "Roads," which fits the clue as a shortened term for those navigation lines. It’s a straightforward abbreviation clue where the answer is a common shorthand in mapping or GPS contexts.