[Geopackage] Query on gpkg_tile_matrix - matrix_width and matrix_height

Even Rouault even.rouault at spatialys.com
Wed Jun 3 05:55:20 EDT 2015

Le mercredi 03 juin 2015 11:41:53, Brad Hards a écrit :
> On Wed, 3 Jun 2015 09:58:39 AM Pepijn Van Eeckhoudt wrote:
> > Yes, that’s the intended usage. gpkg_tile_matrix_set and gpkg_tile_matrix
> > define the grid/matrix/areas where tiles are located. This is orthogonal
> > to presence of data in the user data table.
> Yes.


> > The misleading part in the spec is the use of the word ‘minimum bounding
> > rectangle’. That should probably be removed, but that’s something for the
> > SWG to tackle.
> Yes.


> > If you need to determine the MBR for actually present data you should do
> > a SQL query to select minimum and maximum tile_row and tile_column from
> > the user data table.
> Yes.


(and if the bounding box in gpkg_contents is set, it is generally a better 
hint for the useful bounding box)

> > Note that this is identical to WMTS. gpkg_tile_matrix_set and
> > gpkg_tile_matrix are equivalent to TileMatrixSet and TileMatrix in WMTS.
> > 
> > In WMTS you would use TileMatrixLimits to indicate a sub region of the
> > entire tile structure that actually contains data. GeoPackage doesn’t
> > have this, but you can achieve a similar effect using the SQL query
> > above or the extent in gpkg_contents.
> OK. I tried a WMTS client implementation once. I'd rather not think about
> it again :-)

For the record, I'm working on a GDAL WMTS client that should land into GDAL 
trunk (2.1dev now) soon.

> And I think the corrected "Whitehorse" sample reflects that.  So I'm happy.

I'm noticying strange colours (greenish and pinkish) in 
2015_05_05_Whitehorse_3857.gpkg whereas they looked OK in the original 
ERDC_Whitehorse_GeoPackage.gpkg . Not sure if this is intended or not. It 
seems that the JPEG tiles in the updated package use the uncommon colorspace 
CMYK. I've extracted such a tile and displayed it with various readers and I 
still have the same strange colours

> Brad

Spatialys - Geospatial professional services

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