Ordnance Survey of Northern Ireland (OSNI) has replaced its One-Inch maps with a completely new series at 1:50,000 scale, approximately 1.25 inches to one mile. The series is numbered on an all-Ireland basis and OSNI is responsible for the design and publication of the sheets that cover Northern Ireland and adjoining parts of the Republic of Ireland. The layout incorporates a number of overlaps. The map is derived from the latest large scale material, supplemented by aerial photographs and ground surveys.