Shapefiles and OpenStreetMap data do not overlap in QGIS?

Question

So I'm pretty new to GIS, and I'm working on a mapping project using data for Vancouver, Canada. I want to combine OpenStreetMap data along with data provided by the City of Vancouver. But the City data don't line up with the OSM data when I map them in QGIS.

Following the advice of an answer to Projected maps should but do not overlap in ArcMap?, I checked the two data sources against a third (a map of the world). The OSM data is right -- British Columbia is in the right spot -- but the City data puts Vancouver in the south of France.

My data sources are:

1. Bikeways and libraries from the City of Vancouver. (Both are SHP files.) These are the data that don't align with the others.
2. A map of British Columbia from Open Street Map. I put the data into a database using osm2pgsql.
3. A world map that's part of the Open Street Style project.

Projections:

1. The City data are projected in UTM zone10, NAD83 (CSRS). I've selected this in QGIS's Layer Properties screen for those layers. Projection string: +proj=utm +zone=5 +ellps=GRS80 +datum=NAD83 +units=m +no_defs
2. The OSM maps are in Mercator projection. QGIS has many Mercator choices, and I wasn't sure which one to use, so I guessed "Popular Visualization CRS / Mercator". +proj=merc +lon_0=0 +k=1 +x_0=0 +y_0=0 +a=6378137 +b=6378137 +towgs84=0,0,0,0,0,0,0 +units=m +no_defs
3. For the world map, Quantum GIS loaded the projection from the .prj file. That's +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 +over +no_defs

Projected maps should but do not overlap in ArcMap? talks about zone problems. That sounds like what I might be experienceing. So I tried changing the libraries from UTM zone 10N to other zones (15N and 60N) but nothing changed.

Does anyone have suggestions for what to try next?

Answer 1

What we really have to find out here are the projections of your input data.

1. City data

   The Shapefile comes with a .prj file that is perfectly interpreted by QGIS. Don't change the layer settings!

2. OSM data

   If you are using OSM vector data, they are in WGS84 Geographic coordinates (EPSG:4326). Only the raster tiles are in Web Mercator (EPSG:900913).

3. Open Street Style data

   If QGIS recognized the .prj content, leave it that way.

Finally, chose a project coordinate system (I'd suggest the UTM one) and activate on-the-fly reprojection as @Mike_Toews already explained.

Answer 2

You need to reproject the different layers to the same projection 'on the fly'. Go to:

Settings > Project Properties... > Coordinate Reference System (CRS)

and check on Enable 'on the fly' CRS transformation

Answer 3

I just had this issue adding two rasters, one in UTM and one in Geographic. I followed the directions enabling on the fly projection but nothing happened. I removed the layers, and re-added them and the problem was solved