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I received a .shp file from an ArcGIS user. He said it was in SAD69UTM23S, and indeed it is (checked it in QGIS properties tab). However QGIS is not placing it correctly (using QuickMapServices as reference and other correctly placed .shp files I have; yes OTF reprojection is enabled). I even checked coordinates (of individual points) taken from the attributes table manually converting them and putting in Google Earth, they were equally misplaced.
However, when loaded the original .shp file in Google Earth all the points were in the right places. So I figured it was actually WGS84UTM rather than SAD69 as they said. I changed it in QGIS but it was also misplaced, this time though by a smaller distance.
Is there some kind of compatibility between ArcGIS and Google Earth that doesn't exist between ArcGIS and QGIS?
I don't get it why would Google Earth place the layer correctly but QGIS won't. In fact, apparently Google Earth is using different coordinates for the points (different from those in the attributes table).