World Reference System (WRS). The Path/Row grid.

• WRS-1 — used by Landsat 1–3 (18-day cycle, 251 paths).
• WRS-2 — used by Landsat 4–9 (16-day cycle, 233 paths, 248 rows). Canonical grid for all modern Landsat products.
• WRS makes it possible to cite any place on Earth with a single integer pair and retrieve a consistent scene from any Landsat mission.