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I have access to an ArcGIS Online account. I wanted to create a map with some polygons. So I've used QGIS to make the shapes, saved the layers, zipped them, and uploaded them to ArcGIS Online.

Two days ago my polygons uploaded great and aligned to the basemap perfectly. Using WGS 84 / Pseudo Mercator EPSG:3857 in QGIS worked like a charm (You can see how the shapes border the river very well). FirstUpload

Today I made some revisions to my shapes, including joining some data tables and moving some nodes around. Now when I upload the shapefiles (with the same CRS), everything is misaligned about a mile South of the river. SecondUpload

Here's an overlay if that helps: enter image description here

In QGIS, these two layers overlay as expected. So, what happened?


Here's the results of my .prj file (broken into lines for readability). I have to admit, I have no idea what I'm looking at:

PROJCS["WGS_84_Pseudo_Mercator",GEOGCS["GCS_WGS_1984",DATUM["D_WGS_1984",
SPHEROID["WGS_1984",6378137,298.257223563]],PRIMEM["Greenwich",0],
UNIT["Degree",0.017453292519943295]],PROJECTION["Mercator"],
PARAMETER["central_meridian",0],PARAMETER["false_easting",0],
PARAMETER["false_northing",0],UNIT["Meter",1],
PARAMETER["standard_parallel_1",0.0]]
  • Did you check the projection before uploading the edited shapefile? QGIS can mess up projections easily so you need to be extra careful with them. If global warming lead to a difference of a mile in 2 days I'm pretty sure we'd have noticed by now. – Hasan Mustafa Aug 4 '16 at 5:13
  • @HasanMustafa: according to QGIS, the CRS hasn't changed. Creating the new joins meant I needed to save them as new layers, so there could have been some loss there, but QGIS says they are all WGS 84 / Pseudo Mercator EPSG:3857. Is there a way to check the files themselves? Not sure which file would contain this info. – Chiperific Aug 4 '16 at 18:55
  • Yeah, check the .prj file that accompanies the .shp file. – Thomas Aug 4 '16 at 20:22
  • Updated with PRJ file – Chiperific Aug 5 '16 at 2:13
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QGIS creates two types of projection files with a shapefile. The standard .prj file matches the Esri format and is what you have above. I just created a scratch shapefile and have essentially the same thing. (Breaks added for readability).

PROJCS["WGS_84_Pseudo_Mercator",
GEOGCS["GCS_WGS_1984",
DATUM["D_WGS_1984",
SPHEROID["WGS_1984",6378137,298.257223563]],
PRIMEM["Greenwich",0],
UNIT["Degree",0.017453292519943295]],
PROJECTION["Mercator"],
PARAMETER["central_meridian",0],
PARAMETER["false_easting",0],
PARAMETER["false_northing",0],
PARAMETER["standard_parallel_1",6.64456744726493],
UNIT["Meter",1]]

QGIS also creates a .qpj file with projection information. I am wondering if, perhaps, something happened that the two projection files refer to different CRS? In this scenario, it would be possible for QGIS to reference the .qpj file and Esri products to reference the .prj file.

Here is the .qpj text for the same file noted above. (again, breaks added for readability). I've not looked at documentation on how this is formatted, but would guess that the PROJCS["WGS 84 / Pseudo-Mercator", at the beginning and AUTHORITY["EPSG","3857"] at the end are key things you want to see for a match against the .prj file.

PROJCS["WGS 84 / Pseudo-Mercator",
GEOGCS["WGS 84",DATUM["WGS_1984",
SPHEROID["WGS 84",6378137,298.257223563,
AUTHORITY["EPSG","7030"]],
AUTHORITY["EPSG","6326"]],
PRIMEM["Greenwich",0,AUTHORITY["EPSG","8901"]],
UNIT["degree",0.0174532925199433,AUTHORITY["EPSG","9122"]],
AUTHORITY["EPSG","4326"]],PROJECTION["Mercator_1SP"],
PARAMETER["central_meridian",0],PARAMETER["scale_factor",1],
PARAMETER["false_easting",0],PARAMETER["false_northing",0],
UNIT["metre",1,AUTHORITY["EPSG","9001"]],AXIS["X",EAST],
AXIS["Y",NORTH],
EXTENSION["PROJ4","+proj=merc +a=6378137 +b=6378137 +lat_ts=0.0 +lon_0=0.0 +x_0=0.0 +y_0=0 +k=1.0 +units=m +nadgrids=@null +wktext  +no_defs"],
AUTHORITY["EPSG","3857"]]

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