I've created a map of Bordeaux using the QGIS map compositor by following this procedure:
- Used the OSM plugin to display an OSM map and zoomed to Bordeaux
- Used the print composer to create a map of Bordeax using A4 at full screen
- Added a scale bar, and compared the distance markers with a distance measured in GE between two points in Bordeaux
The two do not agree by quite a lot. The GE measurement for the test area was approximately 1100m, the scale bar suggested the same distance was approximately 1500m.
Is the QGIS scale bar in the print composer supposed to be only approximate? Anyone know if I'm doing something wrong? I don't believe the distance is long enough to worry about possible topography differences.
I've attached a screen shot to show the two measurements: