diff --git a/DDRec/include/DDRec/DetectorData.h b/DDRec/include/DDRec/DetectorData.h
index ae519b3c6dad79dfe52affc72e1614571c341cfc..06d84cbe5628e636c71dcb90775baffb4fcb686f 100644
--- a/DDRec/include/DDRec/DetectorData.h
+++ b/DDRec/include/DDRec/DetectorData.h
@@ -295,14 +295,19 @@ namespace DD4hep {
        */
       int inner_symmetry ;
 
-      /// inner azimuthal angle of the first module in barrel layout
+      /** Angle of the experimental hall floor with the inner face closest to it
+       *  inner_phi0=0 corresponds to a face parallel to the floor
+       */
       double  inner_phi0  ;
       
-      /// outer azimuthal angle of the first module in barrel layout
+      /** Angle of the experimental hall floor with the outer face closest to it
+       *  outer_phi0=0 corresponds to a face parallel to the floor
+       */      
       double  outer_phi0  ;
       
-      /// azimuthal angle of the first module in barrel layout
-      /// DEPRECATED! PLEASE POPULATE INNER/OUTER PHI0 INSTEAD
+      /** Azimuthal angle of the first module in barrel layout
+       *  DEPRECATED! PLEASE POPULATE INNER/OUTER PHI0 INSTEAD
+       */
       double  phi0  ;
       
       /// Gap between modules(eg. stave gap) in the phi-direction