[Requests] Fwd: Geopackage Digest, Vol 26, Issue 1

Jeff Yutzler jeffy at imagemattersllc.com
Thu Mar 2 11:36:03 EST 2017


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From: <geopackage-request at lists.opengeospatial.org>
Date: Wed, Mar 1, 2017 at 12:00 PM
Subject: Geopackage Digest, Vol 26, Issue 1
To: geopackage at lists.opengeospatial.org


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Today's Topics:

   1. Tile gridded elevation data: compulsories entries in
      gpkg_2d_gridded_coverage_ancillary and
      gpkg_2d_gridded_tile_ancillary ? (Even Rouault)


----------------------------------------------------------------------

Message: 1
Date: Wed, 01 Mar 2017 15:48:33 +0100
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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