Mid scale vector polygon dataset showing townland boundaries. Published here for OpenData. The OSNI Largescale Townlands is a polygon dataset consisting of the Townland boundaries. Townlands are an ancient method of land measurement found only in Ireland and can be very important in genealogical research. These small areas of land can vary in size from a few acres upwards. The data has been derived from OSNI Largescale database and has been topologically cleansed and attributed to create a seamless dataset.