Messed up frame annotation in map composer

Question

I am trying to create a nice map figure with lat/lon frame annotation with the map composer. I tried following several tutorials on this and technically it works, however my problem is, that the frame annotation in both lat/lon is completely messed up: it is either centered on zero lat/lon or completely random mixed N+S for lat and E+W values for lon axis. In any way it does not match up with my actual map extent whatsoever and I have no idea why. In the item properties tab the image extents are the right values of my map extent, I did not change the CRS in the "Grids" tab ( it is pseudo mercator) I chose Map unit for interval units and experimented with the "interval" and "offsets", to no success. Settings for grid frame are zebra, left/right divisions: latitude only, top/bottom divisions: longitude only. in the draw coordinates tab: format: degree, minute, second, with suffix and I only enabled left and bottom annotations.

I am running Qgis 2.12.1 on kubuntu 14.04.

Answer 1

If your CRS is psuedo mercator than it's using metres as the map units - so formatting metres as degrees makes no sense. You'd need to set the CRS for the grid to a geographic CRS which uses latitude and longitude, eg 4326. Then the grid units will be in degrees, and formatting them as DMS/etc will work correctly.

Answer 2

So after fumbling around some more with various item properties, I found out that only the coordinate format "decimal" gives the right annotations for lat/lon. Seems qgis is not capable to convert mercator to degree format "on the fly". Also setting the original map's CRS to geographic coordinates did not change this outcome.