[Geopackage] Tile gridded elevation data: compulsories entries in gpkg_2d_gridded_coverage_ancillary and gpkg_2d_gridded_tile_ancillary ?

Jeff Yutzler jeffy at imagemattersllc.com
Thu Mar 2 11:35:49 EST 2017


Even,
I think you're right. I filed
https://github.com/opengeospatial/geopackage/pull/306 in response to
https://github.com/opengeospatial/geopackage/issues/305.
-Jeff

On Wed, Mar 1, 2017 at 12:00 PM, <
geopackage-request at lists.opengeospatial.org> wrote:

> From: Even Rouault <even.rouault at spatialys.com>
> To: geopackage at lists.opengeospatial.org
> Subject: [Geopackage] Tile gridded elevation data: compulsories
>         entries in      gpkg_2d_gridded_coverage_ancillary and
>         gpkg_2d_gridded_tile_ancillary ?
> Message-ID: <1645173.iKvBuibAfx at even-i700>
> Content-Type: text/plain; charset="us-ascii"
>
> Hi,
>
> If I read http://www.geopackage.org/spec/#extension_tiled_gridded_
> elevation_data
> in a pedantic way,
>
> * there's no requirement to insert a new row in gpkg_2d_gridded_coverage_ancillary
> each
> time you have a row in gpkg_contents with datatype = '2d-gridded-coverage'
> . I guess we at least
> need such a row to know if it is a 'integer' or 'float' coverage, but I'm
> not so sure as there are
> sensible default values in the DDL, so it could be assumed to be a
> coverage of type integer,
> with scale = 1, offset = 0, precision = 1 and n nodata.
>
> My current implementation in GDAL would reject such a lack of row in
> gpkg_2d_gridded_coverage_ancillary
>
> * there's no requirement to inset a new row in
> gpkg_2d_gridded_tile_ancillary for each tile
> of the tile pyramid user data table. And that could make sense to not fill
> it if the data is of type
> 'float' or if scale = 1 and offset = 0.
>
> My current implementation in GDAL will accept such missing rows on reading
> (and assume
> tile scale = 1 and tile offset = 0), but will always write them.
>
> Any thoughs about the above: lack of requirements, or are missing rows
> acceptable ?
>
> Thanks,
>
> Even
>
> --
> Spatialys - Geospatial professional services
> http://www.spatialys.com
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-- 
Jeff Yutzler
Image Matters LLC <http://www.imagemattersllc.com/>
Mobile: (703) 981-8753
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