Complex sentence: During the 19th century, an extensive series of maps of Ireland were created by the Irish division of the Ordnance Survey for taxation purposes, which documented and standardised the boundaries of the more than 60,000 townlands in Ireland.
Split into simpler sentences: During the 19th century an extensive series of maps of Ireland was created by the Irish division of the Ordnance Survey for taxation purposes. These maps both documented and standardised the boundaries of the more than 60,000 townlands in Ireland.