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dr-ni / helmert3d

The 3D Helmert transformation is a frequently used method in geodesy to produce transformations between different Cartesian coordinate systems
http://helmparms3d.sourceforge.net/
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Calculate NTV2 grid #14

Open otofoto opened 7 months ago

otofoto commented 7 months ago

Create ntv2 (National Transformation Version 2) grid shift file using Helmert transform from identical point pairs. 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. 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.

Format: https://github.com/Esri/ntv2-file-routines/blob/master/README.md#gsa-file-syntax

zvezdochiot commented 7 months ago

@otofoto . :question: Why are you composting brain? NTv2 is a regular bilinear interpolation or natural neighbour interpolation, which has nothing to do with 7 parameters. Just the values ​​of shifts of one coordinate grid relative to another.

otofoto commented 7 months ago

I mean in case that I do not have identical grids to compare. Took the description from here where 7 parameters are mentioned not sure if it makes sense or is just marketing gimmick: https://www.killetsoft.de/p_ntca_e.htm