[PROJ] Grid CDN Update and Crowdfunding Request

[Chris Crook]

Hi

Sorry I missed the original email thread...

I'm very interested in the possibilities hinted at for GeoTIFF for grid files - but not very clear what capability that would provide.   It sounds like it could provide a way of encoding some aspects of the deformation model we use in NZ.

The specific capability I am hoping for is:

- multiple levels of nested grid
- 1,2, or 3 (more ?) dimensions of data at each grid node (eg de, dn, du,  + possibly uncertainties of each, NTv2 only provides dx/dy and uncertainties of them IIRC)
- values to be floating point or possibly I4 with a defined offset and scale factor for each dimension

Presumably this would also define an interpolation technique (bilinear in each dimension).  NTv2 places what appear to me to be unnecessarily tight constraints on relationships of subgrids with parent grids.  How do you envisage the selection of grid to use at a specific grid cell would be implemented?

I'm also wondering if this could encode more deformation related metadata, such as simple time function parameters (eg step function applying at a certain time, linear ramp between start and end time, or possibly even piecewise linear time function to provide an encoding for post earthquake deformation.

At first sight this looks to provide some very exciting capabilities for time dependent transformations that are going to be needed more and more.

Cheers
Chris

From: PROJ [mailto:proj-bounces at lists.osgeo.org] On Behalf Of Howard Butler
Sent: Wednesday, 13 November 2019 9:39 a.m.
To: PROJ
Subject: [PROJ] Grid CDN Update and Crowdfunding Request

All,

Even has written a crowdfunding page on the CDN and grid files topic at https://www.spatialys.com/en/crowdfunding/ that I had discussed this earlier at https://lists.osgeo.org/pipermail/proj/2019-September/008858.html and its subsequent email thread. The page also provides a detailed proposal (though not in final RFC form) that outlines the technical development activities to achieve the effort. Sponsors have pledged half of the resources to complete this topic, but we still need more resources to bring it over the finish line (or starting line, depending on your perspective). If your organization is interested in helping, please contact me or Even directly.

Howard







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