I am using QGIS for a project.

I have started a new project from scratch within QGIS and have a set of Shape files that were given by the official government authorities.

The problem is that when I use Google Maps or OSM imagery I have a misalignment of about 200 meters, as you can see in the image provided.

enter image description here

I have set the SRC of the project to WGS84 EPSG:4326 so I can work in lat long.

The shape provided is in SRC:

ETRS89 / Portugal TM06 EPSG:3763.

I have also another shape, that is aligned with the previous in the SRC:

Lisboa_Hayford_Gauss_IGeoE EPSG:102164. 

Both the shape files are aligned but not with Google Maps/OSM.

I already tried numerous SRC to fix this problem but it persists.

Am I doing something wrong here?

  • Looks like a projection issue. – HeikkiVesanto Apr 4 '17 at 15:07
  • Probably can't help you without a data sample. – Spacedman Apr 4 '17 at 15:10
  • Possibly check proj.4 strings in the CRS definitions to see what, if any transformations they're using (+wgs84 parameter). It would be great if they're using the Portuguese NTv2 files, but are likely using a 3 or 7 parameter transformation. Edit the question with the information? – mkennedy Apr 4 '17 at 19:46
  • The ETRS89 data should overlay relatively well with the WGS84 data, unless the CRS definition is incorrect. The Lisboa Hayford definition needs a geographic/datum transformation for sure. – mkennedy Apr 4 '17 at 19:47
  • 1
    @Robert datum transformations are expressed in QGIS using the +towgs84 parameters different from zero. Try one of the Portuguese labelled CRS to see if it fits better than ETRS89. – AndreJ Apr 5 '17 at 5:59

The Google Maps layer in QGIS via OpenLayers or QuickMapServices is never 100%, and the best way to use it is to set your map to EPSG 3857 (WGS 84 / Psuedo Mercator aka "Web Mercator")

Keep in mind that you shouldn't depend on the Google Maps layer for much more than a quick reference- you shouldn't be digitizing over this, as you'd be violating Google's terms of service, and I wouldn't be printing anything with Google as the basemap as you'll likely run into more alignment issues.

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