National Grid Reference System for Northern Ireland composed of 292 sheets and provides the naming convention for the 1:10 000 scale mapping. The 10k Grid is published here for Open Data and can be used as a reference system for the download of the DTM and the Mid Scale Raster map. The OSNI 1:10,000 raster grid is referenced to the Irish Grid, with each tile covering a quarter of an Irish Grid sheet. Each tile covers 4.8 km x 3.2 km and there are 1058 tiles covering Northern Ireland.