[OSGeo-Standards] WMTS different <TopLeftCorner> values

Jason Lee jaslee.st at gmail.com
Thu Feb 27 07:38:29 PST 2014

I am setting up a WMTS service with pre-built tiles in a non-Web Mercator
projection (osgb). It has zoom levels which are not always half on each
level, in particular zoom 7 below:-

 * zoom 6 @scale 1:100k,
 * zoom 7 @scale 1:75k,
 * zoom 8 @scale 1:50k
 * zoom 8 @scale 1:25k

I set the <TopLeftCorner> appropriately and things seem to look good when
viewed in QGIS, capabilities XML as follows:-

<TopLeftCorner>0 1433600</TopLeftCorner>

<TopLeftCorner>0 1433600</TopLeftCorner>

<TopLeftCorner>0 1433600</TopLeftCorner>

...but I notice zoom 7 is displayed offset (and same in ArcGIS) and I think
I needed to recalculate the <TopLeftCorner> as I guess it's grid doesn't
"snap" into the grids of the other zoom levels given the same

However, when I change this value just for this TileMatrix, even giving it
a silly value like "<TopLeftCorner>0 0</TopLeftCorner>" it makes no
difference to how the grid aligns at this zoom level.

I found that you have to alter the BOTTOM-MOST TileMatrix (zoom 18) that
makes the grid shift - which is then fine for zoom 7 but ALL the other zoom
levels are offset.

I don't understand why the <TopLeftCorner> value change to zoom 7
TileMatrix does shift this grid alone??

Any help or advice much appreciated, thanks.

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.osgeo.org/pipermail/standards/attachments/20140227/1d4e6433/attachment.html>

More information about the Standards mailing list