Index: trunk/BNC/rinex/rnxobsfile.cpp
===================================================================
--- trunk/BNC/rinex/rnxobsfile.cpp	(revision 3969)
+++ trunk/BNC/rinex/rnxobsfile.cpp	(revision 3970)
@@ -624,5 +624,8 @@
               if (_header._obsTypesV2[i2] == typeV2) {
                 found = true;
-                _indexMap2to3[sys][i2] = i3;
+                map<int, int>::const_iterator it2 = _indexMap2to3[sys].find(i2);
+                if (it2 == _indexMap2to3[sys].end()) {
+                  _indexMap2to3[sys][i2] = i3;
+                }
                 break;
               }