Transformations between the height reference frames: Kronsztadt60, PL-KRON86-NH, PL-EVRF2007-NH

The State Spatial Reference System in Poland currently includes two height reference frames: the first, PL-KRON86-NH, with the old name Kronsztadt'86, and the second, called PL-EVRF2007-NH, as a Polish implementation of the European Vertical Reference Frame (EVRF), named also NAP (Normal Amsterdams Peil). Kronsztadt'86 was supposed to replace the earlier reference system called Kronsztadt'60, but the intentions were not fully in line with reality. Kronsztadt'60 has been implemented in all geodetic and cartographic elaborations even before the computer era and will probably exist until the use of analogue maps or their duplicates in the form of raster maps. For practical purposes, transformation formulas have been developed between all three reference frames mentioned in the title of work. For this purpose, about 16,000 points of the base height network in the PL-EVRF2007-NH and PL-KRON86-NH were used and more than 7,000 points in the Kronsztadt'60. Transformational formulas were developed in two variants: in the form of polynomials approximated by the least squares method and in the form of an interpolative grid. Basic empirical relationships were implemented among others in the program TRANSPOL v. 2.06 [8], elaborated according to the assumptions of the Head Office of Geodesy and Cartography.