[Geopackage] Query on gpkg_tile_matrix - matrix_width and matrix_height

Jeff Yutzler jeffy at imagemattersllc.com
Fri May 29 23:09:44 EDT 2015


Brad,
I am monitoring this but with the OGC meeting next week, it might take a
little while to get the SWG to resolve it. I am going to withhold my
opinion on the matter for the time being.
-Jeff

On Fri, May 29, 2015 at 8:20 PM, Brad Hards <bradh at frogmouth.net> wrote:

> On Fri, 29 May 2015 06:00:24 PM Brachman, Micah wrote:
> > There must be an agreement between the tiles present, and the bounding
> box
> > which will ultimately determine the matrix_height and matrix_width.
>  There
> > ought to be one tile in each of the minimal and maximal rows and
> > columns(There must be a tile at row: 0, column: 0, row: (matrix_height -
> > 1), and column: (matrix_width -1)).  This must hold true at any of the
> zoom
> > levels.  If this doesn't hold true then the bounding box doesn't
> represent
> > the minimum bounds of the data.
> That is contrary to the spec part that says the tiles don't need to be
> present
> at any given zoom level.
>
> The bounding box could describe the potential locations for tiles
> (including
> tiles that haven't been generated / populated yet).
>
> > The data must also comply with the following equations:
> >
> > pixel_x_size = Bounding Box width  * matrix_width  * tile_width
> > pixel_y_size = Bounding Box height * matrix_height * tile_height
> That can't be right. Did you mean to divide at some point, or swap the
> pixel
> and bounding box parts?
>
> Dear SWG: This is looking like a bug in the spec - whatever the real intent
> is/was, it isn't apparent to implementers. Please come to some consensus
> and
> publish a fix.
>
> Brad
>
>


-- 
Jeff Yutzler
Image Matters LLC
Mobile: (703) 981-8753
Office: (703) 428-6731
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.opengeospatial.org/pipermail/geopackage/attachments/20150529/79e23c6b/attachment-0001.html>


More information about the Geopackage mailing list