I'm creating maps with a specified scale for the map window in QGIS Composer. Project CRS is WGS84, layers are WGS84, onthefly-transformation enabled. The area is approx. 1° x 1° (100 x 100 km). But when I measure and calculate the scale manually on the printed map and with the measure tool (metres) in QGIS, the scale is significantly different. The print paper size is the same as set in Composition properties.
Is this a bug or am I doing something wrong??
I'm using QGIS 2.2.0 Valmiera 64bit Win