Index: trunk/BNC/src/combination/bnccomb.cpp
===================================================================
--- trunk/BNC/src/combination/bnccomb.cpp	(revision 10949)
+++ trunk/BNC/src/combination/bnccomb.cpp	(revision 10950)
@@ -1193,4 +1193,20 @@
       it.remove();
       continue;
+    }
+
+    // TEMPORARY DIAGNOSTIC: how far is this epoch from the GLONASS broadcast
+    // ephemeris reference time? t_ephGlo::position() numerically integrates
+    // (Runge-Kutta) from that reference time, with a 24h extrapolation
+    // guard far looser than GLONASS nav's ~30-35 min nominal validity - a
+    // large age here would point to extrapolation-driven along-track error
+    // rather than anything attitude/yaw related.
+    if (corr->_eph->prn().system() == 'R') {
+      double age = epoTime - corr->_eph->TOC();
+      if (fabs(age) > 600.0) {
+        emit newMessage(QString().asprintf(
+          "bncComb: GLONASS eph age %s %.0fs Mjd=%.6f",
+          corr->_prn.mid(0,3).toLatin1().data(), age,
+          epoTime.mjd() + epoTime.daysec()/86400.0).toLatin1(), false);
+      }
     }