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NaturalGIS / naturalgis_ntv2_transformations

A plugin for the QGIS Processing toolbox to allow users do Datum transformations with NTv2 grids
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Add Grid for Germany, Bavaria #45

Open vmarquar opened 4 years ago

vmarquar commented 4 years ago

The Agency for Digitisation, High-Speed Internet and Surveying in Bavaria recently released grid (.gsb) files to perform very accurate transformations between following Coordinate Reference Systems:

GSB Files: The grid spacing is 1 arc second (roughly 30 Meters), which makes the grid file very big (~3Gb). You can find the download links with description at following official site: Information and Download Bavarian Government

Direct link (~1.03 GB): NTV2 Bayern

License: The files are licensed under the Creative Commons Namensnennung-Keine Bearbeitung 3.0 Deutschland (CC-BY-ND). Additionally, the text states that the grid can be used both in internal and external applications.

Is there any chance that you might implement these files for an accurate transformation in Bavaria or are the files to big to be stored on your server?

gioman commented 4 years ago

@vmarquar Hi,

Is there any chance that you might implement these files for an accurate transformation in Bavaria or are the files to big to be stored on your server?

well the size is not important in terms of space occupied on the server, the real issue is that the plugin downloads the GSB files as soon as a specific transformation is run. For grids that are a few KB or MB this adds a little overhead (and just on the first run) but for a GB worth of grids this is probably not acceptable.

I'm not sure if a warning can be added: eventually for this specific transformation we could just document that the grids must be downloaded by hand and uncompressed in a specific folder. This would the simpler and faster solution, yet not the most elegant one. Anyway, as already noticed for other similar request, at the moment we don't have time and resources to add specific transformations in our free time, we can do it for hire if needed. In the most simple case it takes just a few hours of work. Cheers!

gioman commented 4 years ago

at the moment we don't have time and resources to add specific transformations in our free time, we can do it for hire if needed. In the most simple case it takes just a few hours of work. Cheers!

@vmarquar of course eventually feel free to create a pull request with the necessary code to add this transformation, we will apply merge the patch if it checks to be ok.

vmarquar commented 4 years ago

Ok, that might be a good option! I'll take a closer look at your source code when I have some spare time. I think for now I will just stick with plain gdal/ogr to transform my data.