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NTv2Creator geosoftware provides a powerful tool for modelling accurate NTv2 files from identical points in two different Reference Systems. 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 transform 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.
At the beginning of the processing, the coordinates of the identical points are tested for outliers and deviations using statistical methods. Then all grid points are calculated. To calculate a grid point, the program NTv2Creator collects all identical points from the point files of the source reference system and the target reference system, which lie in a certain radius around the grid point. With these points a small spatial three-dimensional 7 parameter Helmert transformation is performed. During the subsequent coordinate transformation of the grid point of the source reference system, the Helmert parameters determine the coordinate of the same grid point in the target reference system. To increase the accuracy the Natural Neighbour interpolation is used for the distribution of the residual gaps. The difference between the coordinates of the grid point in both reference systems is entered as a shift value in the NTv2 file. The calculated shift values include the compensation of regional and local tensions and they consider the different dimensions and bearings of the ellipsoids used in both reference systems.