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I'm seeing a very problematic difference between the size of objects in Google Earth vs the GoogleMAps layer of QuickMapServices (QMS). See the image, the footbridge over the Tyne comes out to 103 m wide in Google Earth but in the same image, QGIS gives it as 183 meters wide. I've had similar scaling isues when creating buffers based on polylines drawn from QMS base maps in QGIS. What I do there is create the vector in WGS84 UTM, digitise on the basemap, then buffer. But this gives sizes that are off by a similar factor to the scaling error in the image above.

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  • That is weird! Wikipedia says ~126m en.wikipedia.org/wiki/Gateshead_Millennium_Bridge , if I measure in QGIS (on OSM Mapnik layer, EPSG:3857) I get ~129m which seems fine for the resolution of OSM. i.imgur.com/WUkpj60.png
    – bugmenot123
    Commented Mar 15, 2017 at 11:19
  • SOLVED! My bad. I had assumed that when opening QMS, the QGIS project CRS would default to Web Mercator. I was wrong and that triggered the string of problems. All fine now.
    – Patrice Carbonneau
    Commented Mar 15, 2017 at 15:22
  • Ha! :) Please add that as answer yourself and accept it so this question is closed.
    – bugmenot123
    Commented Mar 16, 2017 at 9:17

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QMS does not set the project CRS to a default CRS such as Web Mercator, it follows the current project CRS. To work with QMS accurately, you need to manually set your project CRS before you open the basemap using the button in the bottom right of QGIS. From there everything works great.

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