[Geopackage] Query on gpkg_tile_matrix - matrix_width and matrix_height

Even Rouault even.rouault at spatialys.com
Thu May 28 18:54:17 EDT 2015

Hi Brad,

> Geopackage spec ( describes the gpkg_tile_matrix table.
> matrix_width and matrix_height are described as >=1.

Well, Table 9 is a bit more verbose :
matrix_width Number of columns (>= 1) in tile matrix at this zoom level
matrix_height Number of rows (>= 1) in tile matrix at this zoom level

and then Table 10 and req 55 and 56 also give a hint of the meaning.

> The note below Requirement 44 says that there can be records for zoom
> levels that do not have any tiles populated.
> However I can't find an authoritative reference that says what
> matrix_height and matrix_width are intended to describe. I assume that
> they're meant to be a describe the "framework" for the tiles. So if we're
> power of two, and the next higher matrix_width was 2, then this
> matrix_width will be 4 (irrespective of what tiles are actually
> populated).

Not being an authoritative voice, my understanding is that it is not 
For example if you're interested in North America, in GoogleMaps tile matrix 
set, you could have in theory :
level 0 : matrix_width = matrix_height = 1 (world coverage)
level 1 : matrix_width = matrix_height = 1 (top-left quadrant coverage)

since you will never populate other quadrants.

As this was inspired from WMTS, the meaning of matrix_width and matrix_height 
should be the same as WMTS MatrixWidth and MatrixHeight


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