[PROJ] Matrix Library in proj?

[Even Rouault]

Karoline,

Have you considered using the processing you describe to derive a grid or a triangulation that 
would approximate the result your original method gives, within some accuracy you'll 
determine ?

Triangulation-based transformations are an ongoing work, that should be available soon in 
PROJ master.

The details are discussed here:
https://github.com/OSGeo/PROJ/blob/master/docs/source/community/rfc/rfc-6.rst

The implementation considered for inclusion is available at:
https://github.com/rouault/PROJ/tree/tinshift

To answer more specificaly your question about matrix operations, the GDAL library has code 
in
https://github.com/OSGeo/gdal/blob/master/gdal/alg/gdallinearsystem.cpp#L58
to solve a linear problem A . X  = B using LU decomposition

Even

> Hi,
> 
> The Norwegian Mapping Authority is working on getting our old reference
> frame, NGO1948, implemented In proj. The transformation we want to
> implement is the transformation from/to EUREF89 - NGO1948 We already have a
> solution that works, but we have been advised to discuss the use of other
> libraries to solve our problem. Some background information:
> 
> When the Norwegian Mapping Authority introduced the new geodetic datum
> EUREF89, it was necessary to find a proper transformation technique between
> the deprecated geodetic datum NGO1948 to the EUREF89. NGO1948 was
> significant deformed, hereby it was computed and realized in different
> areas of the country. A consequence of this is huge planar gaps in some
> counties and municipalities. The gaps are upon 2-3 meters on borders.
> Description and evaluation of the method are further documented in the
> articles see [OMathisen2002] and [OMathisen2003]. The processing is done in
> three steps: 1. Selection of point pairs
> 2. Deterministic step: 2D Helmert transformation
> 3. Statistic step: Smoothing Least Squared Collocation
> 
> In the solution we have now we have used an open source state of the art
> matrix library (EIGEN3) to compute the Helmert parameters with LSC. This
> process will demand inverting and other matrix operations on large matrices
> (40x40). The size of the matrices are also dynamic.
> 
> At this point there is no matrix library in proj that work with large
> matrices. Does anyone have a suggestion on how we can solve this? Can we
> install external packages or do we have to write our own matrix library, so
> that the library is a part of the source code?
> 
> Best Regards
> 
> Karoline A. Skaar
> Norwegian Mapping Authority
> Tlf./mob.: 32 11 82 16/907 40 302
> E-post: karoline.skar at kartverket.no<mailto:karoline.skar at kartverket.no>
> 
> www.kartverket.no<http://www.kartverket.no/>
> 
> [logo_sign]


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