1) Put the compass folder in the viewer folder.

2) Connection: add this line in the tour.xml file
  <include url="%VIEWER%/compass/compass.xml" />

3) Add the expression ?initvars.setcompas=true to the url in your browser

4) Hit 'C' key and fix compass position while dragging it.
   From the console, insert your correction adjustment in the 'onstart' scene item.
   Example:     <scene name="scene_1" onstart="korrect_comp(-110);" ...

5) Optional:  compass.xml allow to edit the background, risks, text, compass button, etc.

6) Start browsing normaly, without the expression ?initvars...