1

What I am trying to say is:

  1. You import a shapefile into an empty QGIS and the QGIS environment gets the projection system of the imported shapefile.
  2. You import another shapefile into QGIS. The projection system assigned earlier by the previous shapefile remains in place for the QGIS environment.
  3. But, when you import a basemap using the OpenLayers plugin, the environment gets the projection system of the imported basemap.

Why doesn't QGIS just follow one standard by keeping the projection system that was assigned by the first layer imported into its environment?

Note: I have tried this with QGIS 2.10.1 only.

  • 3
    QGIS can reproject vectors on-the-fly and reprojecting local raster maps goes well too. However, reprojecting tiled basemaps is quite different. For utilizing the local cache for the tiles are stored as they come from the service, like a.tile.openstreetmap.org/13/4140/3057.png. It is not impossible to reproject the tiles from the local cache and for example MapProxy mapproxy.org can do that. The writer of the plugin has probably considered that creating a system for reprojecting the tiles is not worth the pain because it is so easy to project vectors to suit with the basemap. – user30184 Sep 16 '15 at 12:57
4

OpenLayers is a plugin and therefore not an integral part of QGIS.

A plugin can modify various parameters of QGIS like the projection. OpenLayers obviously makes use of this possibility.

This is not a conscious decision by the QGIS project but rather a decision by the plugin author which is an external 3rd party.

The best chances for an answer or even a change of this behavior are if you ask the plugin authors directly

4

The OpenLayers plugin overrides your projection preference and set it to EPSG:3857. See Can I use Openlayers Plugin with a different Datum/Projection? : it's due to the tiles providers (Google, Bing, OSM...), not to QGIS.

  • When opening an OSM map in ArcMap, the CRS of the ArcMap environment is not affected. – multigoodverse Sep 16 '15 at 12:55
  • Are you talking about opening a vector layer or a raster layer like with a WMS or TMS ? – jeremy g Sep 16 '15 at 13:04

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