A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: Ronald van Riet
Date: 2018 Sep 24, 01:30 -0700
The accuracy actually is half a meter: if the offset would have been more than a half meter, the next position would have been specified).
The Dutch RD (Rijskdriehoekmeting) grid is based on a church tower in Amersfoort (http://www.waymarking.com/waymarks/WMG9A7_RD_Meetpunt_32910101_Amersfoort) being the central point and this location is known with very high precision. The actual zero point lies off the coast of France so all coordinates in The Netherlands are always positive.
And the nails that are struck in the ground have been positioned on the exact meter offset from Amersfoort, so their position aty least is very accurate to within a centimeter or so.
The church towers and similar points of course are accurate to within a half meter.
PS. For benchmarks in other countries, please visit http://www.waymarking.com/cat/details.aspx?f=1&guid=905a74da-86b5-430d-94fb-d8be675283f7