[OSGeo-Standards] WMTS and TMS opposing grid origins (top-left vs bottom-left)
jaslee.st at gmail.com
Tue Dec 10 03:12:51 PST 2013
I can understand the reason why the top-left is the origin but was hoping
the standard was perhaps flexible enough to allow setting of alternative
origins given the historical reference to TMS.
I've actually setup a rewrite rule at the tile server to "invert" the
y-value to handle the difference so it is not such an issue now (only
slight calculation overhead on the server).
On 6 December 2013 17:09, Raj Singh <rsingh at opengeospatial.org> wrote:
> I asked some of the WMTS experts in OGC and here's a paraphrase of the
> response I received.
> "Integer-based coordinate systems are usually oriented starting 0,0 at the
> top left. It especially makes sense when they're meant to be linearly
> mapped to screen/image pixel coordinates (which has 0,0 at the top left).
> It's the way WMS GetFeatureInfo I,J is oriented, and the way Google Maps
> tiles are oriented. I believe it's also the way ArcGISMap tiles are
> oriented. TMS appears to be the exception."
> The OGC: Making location count.
> On Dec 5, at 5:06 AM, Jason Lee <jaslee.st at gmail.com> wrote:
> > Hi,
> > I've set up some map tiles in a non-Web Mercator projection and have
> rendered them with tile numbering starting in the bottom-left - just like
> that in the TMS format and suitable custom scales (NOT half on each
> successive zoom level).
> > I've be able to successfully consume the tiles in an OpenLayers
> client..However, I've been looking at how we can bring these tiles into
> ArcGIS desktop via WMTS and I see that this OGC standard assumes a grid
> origin starting at the top-left - is that right? ...my tiles are mixed up
> when attempting to consume them in ArcGIS.
> > Why does WMTS have tile number origin at the top-left when the previous
> TMS started in bottom-left? Is there syntax in WMTS to make it start in
> bottom-left like in TMS?
> > Thanks
> > Jason
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