What Are Grid References?
A grid reference is a way to describe an exact location on a map. Maps are printed with a network of horizontal and vertical lines forming a grid. Each line is given a number.
The vertical lines running from top to bottom are called eastings (they increase as you go east). The horizontal lines running left to right are called northings (they increase as you go north).
Four-Figure Grid References
A four-figure grid reference identifies a grid square — the 1 km × 1 km box to the right of and above the given lines.
Example: Grid reference 3452 means:
- Easting 34 (the vertical line numbered 34)
- Northing 52 (the horizontal line numbered 52)
- The square is immediately to the right of line 34 and above line 52.
Six-Figure Grid References
A six-figure reference pinpoints a location even more precisely within a square by imagining the square divided into 10 × 10 smaller parts.
Example: Grid reference 342524 means:
- Easting 342 — 2 tenths across square 34
- Northing 524 — 4 tenths up square 52
Why Grid References Matter
Emergency services, hikers, and geographers all use grid references to communicate locations without ambiguity. Saying "the barn at grid reference 452718" gives a far more precise location than just describing a town or village.
Real world: Mountain Rescue and grid references
Mountain Rescue teams in the UK and Ireland rely on grid references to coordinate rescue operations in remote terrain. When a hiker calls 999 and reports being injured on a hillside, the first question is often "what's your grid reference?" A six-figure OS grid reference locates them to within 100 metres. Since 2015, the What3Words app has complemented this by dividing the entire Earth into 3 m × 3 m squares, each with a unique three-word address — used by emergency services in over 100 countries. However, traditional grid references remain the standard for official UK mapping.
Real world: Military navigation and grid references
Military forces worldwide use grid references (similar to the UK OS system) for tactical communication. NATO uses the Universal Transverse Mercator (UTM) system, which divides the world into grid squares. Soldiers use military grid references to call in artillery fire, coordinate air support, and navigate without relying on electronics that could be jammed or fail. The 2003 Iraq War saw extensive use of GPS alongside paper map grid references — when GPS signals were temporarily disrupted, units fell back on map skills.
Real world: Planning applications and ordnance survey grid references
When a UK planning application is submitted to a local council — for a new house, wind turbine, or supermarket — it must include the OS National Grid reference of the proposed site. This allows planners, environmental agencies, and neighbours to identify the exact location on official maps. Grid references are also used by the Environment Agency to map flood risk zones, helping decide whether planning permission should be granted near rivers or coasts.
Where do you see this in real life? Download the OS Maps app or use grid ref tools online. Find your school or home on the map and look up its six-figure grid reference. Emergency services use exactly this system when responding to incidents — if you are ever lost in the countryside, knowing your grid reference could save your life.
Practice Problems
A map has eastings and northings. What four-figure grid reference describes the square immediately to the right of line 27 and above line 41?
Show answer
Why do we read the easting before the northing when giving a grid reference?