I'm trying to understand tilesorigin and Meta-tiling in GeoServer.
The docs state that tilesorigin=x,y where x and y are the coordinates of the lower left corner (the “origin”) of the tile grid system.
And gives (OpenLayers 2) example: tilesorigin: map.maxExtent.left + ',' + map.maxExtent.bottom
Is the equivalent for modern OpenLayers either one of the below?
ol.extent.getBottomLeft(ol.proj.get('EPSG:3857').getExtent()).toString()
ol.extent.getBottomLeft(map.getView().getProjection().getExtent()).toString()
How do I know if meta-tiling is actually working? Tiling and caching of tiles works fine without setting tilesorigin.
What is a logic of requiring the client sets tiled=true and tilesorigin to enable meta-tiling? If one client makes requests with tilesorigin omitted (meta-tiling disabled), and the tiles that are generated are cached, and a different client makes requests with tilesorigin set correctly (meta-tiling enabled), the second client will just get back the cached tiles created by the first client, and not get the benefit of meta-tiling?
If GeoServer knows a client making requests with srs=EPSG:3857, and bottomleft of EPSG:3857 is always the same, why doesn't it just figure out tilesorigin itself, and not rely on the client correctly setting it?
Best Answer
These parameters are a hack put in to help early WMS clients get the benefit of tiles with out them having to understand the WMTS standard.
You shouldn't need to use them these days as OpenLayers and Leaflet (and most other clients) understand WMTS and TMS tiling. So, they can make requests in a better fashion that GeoServer (GeoWebCache) understands with out any effort at either end.