diff --git a/Library/ADSB.cpp b/Library/ADSB.cpp
index fb37f25169..6cdd2c6af1 100644
--- a/Library/ADSB.cpp
+++ b/Library/ADSB.cpp
@@ -456,7 +456,7 @@ namespace Plane
         double lon_final = use_even ? even.lon : odd.lon;
 
         ln = (90.0 / ni) * (MOD(m, ni) + lon_final / CPR_SCALE);
-        ln -= 90.0 * std::floor((lon - ref_lon + 45.0) / 90.0);
+        ln -= 90.0 * std::floor((ln - ref_lon + 45.0) / 90.0);
 
         latlon_timestamp = use_even ? even.timestamp : odd.timestamp;
         updated = true;
diff --git a/Library/ADSB.h b/Library/ADSB.h
index 340e27f480..494d1d0a29 100644
--- a/Library/ADSB.h
+++ b/Library/ADSB.h
@@ -73,6 +73,15 @@ namespace Plane
         LL time_ll;
         LL hash_ll;
 
+        struct
+        {
+            FLOAT32 lat, lon;
+            std::time_t timestamp;
+            struct Plane::CPR cpr;
+            bool even;
+        } CPR_history[3];
+        int CPR_history_idx = 0;
+
         uint8_t msg[14]; // Raw message
         int df;          // Downlink format
         int msgtype;     // Message type
@@ -143,6 +152,12 @@ namespace Plane
             message_subtypes = 0;
             position_status = ValueStatus::UNKNOWN;
 
+            for(int i = 0; i < 3; i++) {
+                CPR_history[i].cpr.clear();
+                CPR_history[i].lat = LAT_UNDEFINED;
+                CPR_history[i].lon = LON_UNDEFINED;
+            }
+
             crc = CRC_UNDEFINED;
             status = STATUS_OK;
             country_code[0] = country_code[1] = ' ';
diff --git a/Tracking/PlaneDB.h b/Tracking/PlaneDB.h
index f8cd8e74fb..d4a7b9fc1e 100644
--- a/Tracking/PlaneDB.h
+++ b/Tracking/PlaneDB.h
@@ -14,15 +14,6 @@ class PlaneDB : public StreamIn<Plane::ADSB>
     const int END = -1;
     const int FREE = -2;
 
-    struct
-    {
-        int lat, lon;
-        std::time_t timestamp;
-        struct Plane::CPR cpr;
-        bool even;
-    } CPR_history[3];
-    int CPR_history_idx = 0;
-
 private:
     int first = -1;
     int last = -1;
@@ -293,39 +284,51 @@ class PlaneDB : public StreamIn<Plane::ADSB>
                 if (std::fabs(plane.lat - lat_new) > 0.1 || std::fabs(plane.lon - lon_new) > 0.1)
                 {
                     plane.position_status = Plane::ValueStatus::UNKNOWN;
-                    //std::cerr << "Inconsistent position for " << std::hex << plane.hexident << std::dec << std::endl;
                 }
             }
 
+            plane.position_status = Plane::ValueStatus::VALID;
+
             // store the history of the last 3 CPR positions
-            CPR_history[CPR_history_idx].lat = lat_new;
-            CPR_history[CPR_history_idx].lon = lon_new;
-            CPR_history[CPR_history_idx].even = msg->even.Valid();
-            CPR_history[CPR_history_idx].cpr = msg->even.Valid() ? plane.even : plane.odd;
+            plane.CPR_history[plane.CPR_history_idx].lat = lat_new;
+            plane.CPR_history[plane.CPR_history_idx].lon = lon_new;
+            plane.CPR_history[plane.CPR_history_idx].even = msg->even.Valid();
+            plane.CPR_history[plane.CPR_history_idx].cpr = msg->even.Valid() ? plane.even : plane.odd;
 
             if (plane.position_status == Plane::ValueStatus::UNKNOWN)
             {
                 // check for consistency with independent position
-                int prev = (CPR_history_idx + 2) % 3;
-                int indepedent = (CPR_history_idx + 1) % 3;
+                int prev = (plane.CPR_history_idx + 2) % 3;
+                int indepedent = (plane.CPR_history_idx + 1) % 3;
 
-                if (CPR_history[prev].cpr.Valid() && CPR_history[CPR_history_idx].cpr.Valid() && CPR_history[CPR_history_idx].even != CPR_history[prev].even)
+                if (plane.CPR_history[prev].cpr.Valid() && plane.CPR_history[plane.CPR_history_idx].cpr.Valid() && plane.CPR_history[plane.CPR_history_idx].even != plane.CPR_history[prev].even)
                 {
-                    if (CPR_history[indepedent].cpr.Valid())
+                    if (plane.CPR_history[indepedent].cpr.Valid())
                     {
-                        FLOAT32 distance = DISTANCE_UNDEFINED;
-                        int angle = ANGLE_UNDEFINED;
-                        getDistanceAndBearing(CPR_history[indepedent].lat, CPR_history[indepedent].lon, lat_new, lon_new, distance, angle);
-                        
-                        if (distance < 500)
+                        // check against last independent position, i.e. with different CPR pair
+                        double deltat = 1 - plane.CPR_history[indepedent].cpr.timestamp + plane.CPR_history[plane.CPR_history_idx].cpr.timestamp;
+
+                        if (deltat < 15 * 60)
                         {
-                            plane.position_status = Plane::ValueStatus::VALID;
+                            FLOAT32 distance = DISTANCE_UNDEFINED;
+                            int angle = ANGLE_UNDEFINED;
+                            getDistanceAndBearing(plane.CPR_history[indepedent].lat, plane.CPR_history[indepedent].lon, lat_new, lon_new, distance, angle);
+             
+                            double deltat = 1 - plane.CPR_history[indepedent].cpr.timestamp + plane.CPR_history[plane.CPR_history_idx].cpr.timestamp;
+                            double speed = plane.speed == SPEED_UNDEFINED ? 1000 : plane.speed * 1.5;
+                            double max_distance = deltat * speed / 3600.0;
+
+                            std::cerr << "Distance: " << distance << " Max: " << max_distance << std::endl;
+                            if (distance < max_distance)
+                            {
+                                plane.position_status = Plane::ValueStatus::VALID;
+                            }
                         }
                     }
                 }
             }
 
-            CPR_history_idx = (CPR_history_idx + 1) % 3;
+            plane.CPR_history_idx = (plane.CPR_history_idx + 1) % 3;
 
             if (plane.position_status == Plane::ValueStatus::VALID)
             {