Modelling of NTv2 files from Identical Points in two Reference Systems.
With the program NTv2Creator experts in geodesy and surveying have access to an economical standard software, that allows them to generate accurate NTv2 solutions by themselves.
Kempen, August 14, 2020
Dipl.-Ing. Fred Killet - Killet GeoSoftware Ing.-GbR - Escheln 28a - 47906 Kempen, Germany
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NTv2 stands for National Transformation Version 2 and describes a procedure for the transformation of georeferenced data from one reference system to another. Today, the NTv2 procedure is integrated in all GIS and transformation programs, so that it can be used to perform high-precision coordinate transformations, for example in the context of the INSPIRE implementation.
So the use of already existing NTv2 files is no problem. But how is a new NTv2 file created from a cloud of irregularly distributed geodetic points? First of all, all points must be available as so-called identical points which have been accurately measured and calculated in two different reference systems. From the identical points, the shift values of the grid points for a defined working area are elaborately calculated in a one-time process and stored in an NTv2 file as a regular grid. This process has so far been done by a few engineering companies that have the know-how. As experience has shown, the costs for modelling NTv2 files are very high.
With the new geosoftware NTv2Creator KilletSoft provides an economically priced and powerful tool for the autonomous modelling of exact NTv2 files from identical points. The software analyses two files with identical points and suggests the boundaries and mesh sizes which can then be changed manually. Finally, a highly accurate NTv2 file is generated using small-scale three-dimensional 7-parameter Helmert transformations around each grid point and subsequent Natural Neighbour Interpolation for residual gap distribution. NTv2Creator provides three different mathematical models for the modelling of NTv2 files in ASCII format (gsa) and in binary format (gsb). To assess the quality of the newly modelled NTv2 file, it is checked by cross-calculation and the result is stored in a cluster field. Bad matching identical points are determined and suggested for rectification.
Detailed information about the program NTv2Creator can be found on the website  https://www.killetsoft.de/p_ntca_e.htm. There you can also download a free but restricted test version. The licensed full version without restrictions is currently offered at an attractive launch price.