There is a stone block on an earlier Meridian by the railings of the courtyard about six metres to the left of the sculpture. This Meridian Line is called the Bradley Meridian and is defined by an earlier telescope, which is also in place inside the Meridian building. It was used between 1750 and 1850. The Ordnance Survey first mapped the UK during this time. They used the Bradley Meridian as their zero reference for measuring east and west. The Bradley Meridian is still used for Ordnance Survey maps today. The stone block supported a marker for carrying out simple alignment checks with the telescope. It was placed here in 1798.