[PROJ] Preferred grid format for transformations?

[Chris Crook]

Hi Brian

Also picking up on this  - for a while Land Information New Zealand (LINZ) has been looking for a suitable format for publishing our deformation model - essentially a 3d time dependent transformation model.  This includes both a secular velocity model as well as 3d deformation grids for significant earthquakes.

I am writing a  proposal for extending the GeoTIFF format to fully encode this transformation - I hope to submit this proposal as a document for comment to this list by the end of this week.  The functional model LINZ uses for deformation is relatively simple and generalised - what I am hoping is that the format will be useful beyond LINZ usage.  This proposal essentially adds some metadata to the GeoTIFF format that defines how the component grids are used to determine the point displacements at any time.

Cheers
Chris


> -----Original Message-----
> From: PROJ [mailto:proj-bounces at lists.osgeo.org] On Behalf Of Even
> Rouault
> Sent: Tuesday, 26 November 2019 10:10 a.m.
> To: proj at lists.osgeo.org
> Subject: Re: [PROJ] Preferred grid format for transformations?
>
> Brian,
>
> > The National Geodetic Survey is considering changes to the grids we
> > output for transformations, geoids and more and I was wondering if
> > there are currently any preferred or ideal grid formats in the PROJ
> > community?  I have been doing a little research as well as seen a few
> > threads recently that mentioned GeoTiff, NetCDF and HDF5 but wanted to
> > see if you guys had any preferences?
>
> This is indeed a "hot" topic. I've submitted today a Request for Comments to
> the PROJ (and larger) community, whose one of the main topics is a
> discussion about adopting a GeoTIFF format:
> https://github.com/rouault/PROJ/blob/rfc4_remote_and_geotiff_grid/docs
> /source/community/rfc/rfc-4.rst#grids-in-geotiff-format
>
> > A few things that will be coming in 2022 include grids for 3D
> > velocities, uncertainties for grids (geoids, transformations) and more
> > so some of the things discussed like having multidimensional
> > information at each node would be nice.
>
> I assume here that by "multidimensional" you mean storing several samples
> per grid node, where the grid is still 2D indexed (referenced to a geographic
> longitude, latitude CRS
> typically) ?
> The above GeoTIFF proposal should be able to allow this.
>
> Even
>
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