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Hope this isn't a duplicate, did some searching but none seemed quite the same.

Projection I want: WGS84/Pseudo-mercator. Selected. Looks Great.

Canvas units I want: Decimal Degress. Selected. Denied. Assumed reason: WGS84/Pseudo_Mercator's CRS code is:

+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

I assume the units argument is over-riding the user's canvas units choice?

Is there any way around this? I don't know how to create a custom CRS but if it's easy enough to do, would it just be a case of copying the line above and omitting the bold bit?

Thanks!!

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Projected coordinate systems always have metres or feet as units. CRS with degrees are called Geographic coordinate systems. Pseudo-Mercator does not belong to them.

The only thing you can have in QGIS are degree grids over your Pseudo-Mercator map:

How to display both scalebar in kilometers and grid in lat/long degrees in Quantum GIS 1.8 Composer?

Is there lat/lon grid option in QGIS?

The Coordinate Capture plugin allows you to see the degrees (if CRS is set to WGS84).

  • Thanks Andre - I didn't realise QGis wouldn't allow this, and thanks for the graticule ideas. I'm surprised, though, that it's not allowed given that projected coordinate systems are still representations of the earth, and thus the position of the cursor necessarily corresponds to a point on the earth which has a geographic coordinate... Do you know if the reason is simply that the code to calculate the conversion hasn't been done, or is there a fundamental reason/principle I'm not grasping? Cheers. – dez93_2000 Jan 16 '14 at 11:45
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    QGIS shows the coordinates in the same way they are displayed. Google display the geographic coordinates, which might be better known by the end user. The coordinate capture plugin allows you to see the degrees (if chosen WGS84). – AndreJ Jan 16 '14 at 11:59
  • Sorry Andre, not sure what you mean by the first line - show & display are rather synonymous! Do you mean in specific places? Thanks for the coordinate capture tip, that does the trick (decimal degrees in PM projection). Just seems a shame that QGis doesn't give the option to do that natively in the default coordinate box... – dez93_2000 Jan 16 '14 at 12:31
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    The pixels painted in the canvas are placed using projected coordinates, and the coordinate box only shows those. Independent from the geographic coordinates behind it. This will also work if you have no valid CRS information. – AndreJ Jan 16 '14 at 12:47
  • ... and think of projections like orthographic where parts of the canvas fall outside the globe (see my avatar picture for reference). – AndreJ Jan 16 '14 at 13:41

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