I'm trying to visualise/convert EPSG:3857 map tiles to EPSG:4326, but am experiencing strange behavior in that I don't think the most zoomed out view of the world is using the correct CRS/Auth ID.

EDIT: this behavior only seems to occur when using XYZ map tiles. If testing with the Natural Earth vector data, it is displayed correctly at all zoom levels. Overlaying the XYZ map tiles over the Natural Earth data show the same disparity (i.e. the tiles seem top-bottom squashed).

To replicate this (strange to me) behavior:

  1. Create a new QGIS 3 project
  2. Load in XYZ tiles (e.g. one of: ESRI Standard, Google Maps, OpenStreetMap standard)
  3. Set Project CRS (in bottom right) to EPSG:4326
  4. (Optional) Right click raster tile layer, and 'Zoom to Layer'
  5. If you then zoom in (with a single scroll wheel click) to say Brazil, or Africa, its shape significantly changes. Subsequent zooms seem to work as expected.
  6. Also, plotting EPSG:4326 data at the most zoomed out level seems to put things in the wrong place. Upon zooming in, they jump to the right place.

My questions:

  • Why is the CRS/Auth ID of the most zoomed out image (Fig 1) not EPSG:4326?
  • Is this behavior to be expected? Is it a bug in QGIS? Is there a workaround (to make the initial overall world view correct)?

Fig 1: Example of zoomed out image: Example of zoomed out image:

Fig 2: Example after single scroll wheel click, to zoom in: enter image description here

  • If you zoom out again after the first scroll did the display revert to the wrong view ? – J.R Jan 17 '19 at 12:30
  • @J.R Yes, zooming again out takes me back to the wrong view – Jonny Jan 17 '19 at 14:12
  • 1
    An interesting discussion on this topic can be read here. – Gabriel De Luca Jan 17 '19 at 23:25

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