First, I would like to apologize for the mistakes. My English is not very good. I read a lot but I don´t find the answer. I'm trying to put a scalebar in a very simple map but the measurement is not correct. I'm going to describe the process (spanis version 2.10.1):
1) I open QGis -> project -> properties
2) General -> measurement tool WGS84 (SRC transformation connected)
3)SRC on the fly activated (SRC 3857 and also tried with 4326 similar results)
4) New Shapefile -> line shapefile -> I create a line of 10.000 m length (measured with the qgis measurement tool)
5) Print composer -> new map -> escale ej 1:10.000 -> add scale bar.
6) Export to PDF
7)I print the map (from PDF to printer with pdf not scaled) and the scale with the scalebar and is not correct