diff --git a/doc/Conversions.odt b/doc/Conversions.odt
index 9ca2adb..d6c662c 100644
Binary files a/doc/Conversions.odt and b/doc/Conversions.odt differ
diff --git a/doc/Conversions.pdf b/doc/Conversions.pdf
index 3de736b..06bf6f2 100644
Binary files a/doc/Conversions.pdf and b/doc/Conversions.pdf differ
diff --git a/lib/nmea0183ton2k/NMEA0183DataToN2K.cpp b/lib/nmea0183ton2k/NMEA0183DataToN2K.cpp
index cf335df..0560375 100644
--- a/lib/nmea0183ton2k/NMEA0183DataToN2K.cpp
+++ b/lib/nmea0183ton2k/NMEA0183DataToN2K.cpp
@@ -638,8 +638,8 @@ private:
         for (int i=0;i< 3;i++){
             if (msg.FieldLen(0)>0){
                 Depth=atof(msg.Field(0));
-                char dt=msg.Field(i+1)[0];
-                switch(dt){
+                char du=msg.Field(i+1)[0];
+                switch(du){
                     case 'f':
                         Depth=Depth/mToFeet;
                         break;
@@ -662,8 +662,9 @@ private:
                 //we can only send if we have a valid depth beloww tranducer
                 //to compute the offset
                 if (! boatData->DBT->isValid()) return;
-                double offset=Depth-boatData->DBT->getData();
-                if (offset >= 0 && dt == DBT){
+                double dbs=boatData->DBT->getData();
+                double offset=Depth-dbs;
+                if (offset >= 0 && dt == DBK){
                     logger->logDebug(GwLog::DEBUG, "strange DBK - more depth then transducer %s", msg.line);    
                     return;
                 }
@@ -675,8 +676,8 @@ private:
                     if (! boatData->DBS->update(Depth,msg.sourceId)) return;
                 }
                 tN2kMsg n2kMsg;
-                SetN2kWaterDepth(n2kMsg,1,Depth,offset);
-                send(n2kMsg,msg.sourceId,(n2kMsg.PGN)+String((offset != N2kDoubleNA)?1:0));
+                SetN2kWaterDepth(n2kMsg,1,dbs,offset); //on the N2K side we always have depth below transducer
+                send(n2kMsg,msg.sourceId,(n2kMsg.PGN)+String((offset >=0)?1:0));
             }            
         }        
     }
diff --git a/lib/nmea2kto0183/N2kDataToNMEA0183.cpp b/lib/nmea2kto0183/N2kDataToNMEA0183.cpp
index afafcd6..dbf6af5 100644
--- a/lib/nmea2kto0183/N2kDataToNMEA0183.cpp
+++ b/lib/nmea2kto0183/N2kDataToNMEA0183.cpp
@@ -267,21 +267,29 @@ private:
         double DepthBelowTransducer;
         double Offset;
         double Range;
-        double WaterDepth;
         if (ParseN2kWaterDepth(N2kMsg, SID, DepthBelowTransducer, Offset, Range))
         {
-
-            WaterDepth = DepthBelowTransducer + Offset;
-            updateDouble(boatData->DBS, WaterDepth);
-            updateDouble(boatData->DBT,DepthBelowTransducer);
-            tNMEA0183Msg NMEA0183Msg;
-            if (NMEA0183SetDPT(NMEA0183Msg, DepthBelowTransducer, Offset,talkerId))
+            if (updateDouble(boatData->DBT, DepthBelowTransducer))
             {
-                SendMessage(NMEA0183Msg);
-            }
-            if (NMEA0183SetDBx(NMEA0183Msg, DepthBelowTransducer, Offset,talkerId))
-            {
-                SendMessage(NMEA0183Msg);
+                tNMEA0183Msg NMEA0183Msg;
+                bool offsetValid=true;
+                if (N2kIsNA(Offset)) {
+                    Offset=NMEA0183DoubleNA;
+                    offsetValid=false;
+                }
+                if (NMEA0183SetDPT(NMEA0183Msg, DepthBelowTransducer, Offset, talkerId))
+                {
+                    SendMessage(NMEA0183Msg);
+                }
+                if (offsetValid)
+                {
+                    double WaterDepth = DepthBelowTransducer + Offset;
+                    updateDouble(boatData->DBS, WaterDepth);
+                }
+                if (NMEA0183SetDBx(NMEA0183Msg, DepthBelowTransducer, Offset, talkerId))
+                {
+                    SendMessage(NMEA0183Msg);
+                }
             }
         }
     }