The Ordnance Survey grid system, a form of map coordinates in the UK. https://www.ordnancesurvey.co.uk/resources/maps-and-geographic-resources/the-national-gri

The Ordnance Survey grid system, a form of map coordinates in the UK. https://www.ordnancesurvey.co.uk/resources/maps-and-geographic-resources/the-national-grid.html https://www.ordnancesurvey.co.uk/resources/maps-and-geograph... https://en.wikipedia.org/wiki/Ordnance_Survey_National_Grid https://en.wikipedia.org/wiki/Ordnance_Survey_National_Grid