NAP network

• The high-precision levelling network (NAP) of Bizkaia is part of the geodetic infrastructure of the Historical Territory of Bizkaia. It densifies the REDNAP Project of the National Geographic Institute (IGN), which in turn links up with the EUVN European vertical reference models. The new sections being carried out by the BFA/DFB are consistent with the specifications and qualities of the IGN's REDNAP. The Historical Territory of Bizkaia therefore has a heterogeneous network of levelling signals in which IGN nails, new DFB nails and Basque Government nails (in altimetric frames not in force) survive and are being re-observed in the NAP densification campaigns.