[OSGeo-Standards] WMTS and TMS opposing grid origins (top-left vs bottom-left)
rsingh at opengeospatial.org
Fri Dec 6 09:09:10 PST 2013
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:
> 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?
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