diff --git a/libraries/AP_NavEKF/AP_Nav_Common.h b/libraries/AP_NavEKF/AP_Nav_Common.h
new file mode 100644
index 0000000000..06bcae194c
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+++ b/libraries/AP_NavEKF/AP_Nav_Common.h
@@ -0,0 +1,36 @@
+/// -*- tab-width: 4; Mode: C++; c-basic-offset: 4; indent-tabs-mode: nil -*-
+/*
+  AP_Nav_Common holds definitions shared by inertial and ekf nav filters
+
+  This program is free software: you can redistribute it and/or modify
+  it under the terms of the GNU General Public License as published by
+  the Free Software Foundation, either version 3 of the License, or
+  (at your option) any later version.
+
+  This program is distributed in the hope that it will be useful,
+  but WITHOUT ANY WARRANTY; without even the implied warranty of
+  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+  GNU General Public License for more details.
+
+  You should have received a copy of the GNU General Public License
+  along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#ifndef AP_Nav_Common
+#define AP_Nav_Common
+
+union nav_filter_status {
+    struct {
+        uint8_t attitude        : 1; // 0 - true if attitude estimate is valid
+        uint8_t horiz_vel       : 1; // 1 - true if horizontal velocity estimate is valid
+        uint8_t vert_vel        : 1; // 2 - true if the vertical velocity estimate is valid
+        uint8_t horiz_pos_rel   : 1; // 3 - true if the relative horizontal position estimate is valid
+        uint8_t horiz_pos_abs   : 1; // 4 - true if the absolute horizontal position estimate is valid
+        uint8_t vert_pos        : 1; // 5 - true if the vertical position estimate is valid
+        uint8_t terrain_alt     : 1; // 6 - true if the terrain height estimate is valid
+        uint8_t const_pos_mode  : 1; // 7 - true if we are in const position mode
+    } flags;
+    uint8_t value;
+};
+
+#endif // AP_Nav_Common