From information supplied Primary benchmark was taken as R 31 1.660m relative to TGZ. Giving a RLR factor of 8.040m. Currently sea level is recorded downwards. Other benchmarks are: R 20 YY 1.082m relative to TGZ R 10 YY 0.485m relative to TGZ RGYS 0.285m relative to TGZ Spike Feb 2008 but this is mirrored in Preveza when the data are buddy checked.
Hellenic Navy Hydrographic Service Geographic Policy and International Relations Office TGN 1040 Athens