diff --git a/libraries/AP_NavEKF3/AP_NavEKF3_AirDataFusion.cpp b/libraries/AP_NavEKF3/AP_NavEKF3_AirDataFusion.cpp
index c0ea29f1dd..13d6e94aea 100644
--- a/libraries/AP_NavEKF3/AP_NavEKF3_AirDataFusion.cpp
+++ b/libraries/AP_NavEKF3/AP_NavEKF3_AirDataFusion.cpp
@@ -95,7 +95,7 @@ void NavEKF3_core::FuseAirspeed()
 
         if (!inhibitDelVelBiasStates && !airDataFusionWindOnly) {
             for (uint8_t index = 0; index < 3; index++) {
-                uint8_t stateIndex = index + 13;
+                const uint8_t stateIndex = index + 13;
                 if (!dvelBiasAxisInhibit[index]) {
                     Kfusion[stateIndex] = SK_TAS[0]*(P[stateIndex][4]*SH_TAS[2] - P[stateIndex][22]*SH_TAS[2] + P[stateIndex][5]*SK_TAS[1] - P[stateIndex][23]*SK_TAS[1] + P[stateIndex][6]*vd*SH_TAS[0]);
                 } else {
@@ -394,7 +394,7 @@ void NavEKF3_core::FuseSideslip()
 
         if (!inhibitDelVelBiasStates && !airDataFusionWindOnly) {
             for (uint8_t index = 0; index < 3; index++) {
-                uint8_t stateIndex = index + 13;
+                const uint8_t stateIndex = index + 13;
                 if (!dvelBiasAxisInhibit[index]) {
                     Kfusion[stateIndex] = SK_BETA[0]*(P[stateIndex][0]*SK_BETA[5] + P[stateIndex][1]*SK_BETA[4] - P[stateIndex][4]*SK_BETA[1] + P[stateIndex][5]*SK_BETA[2] + P[stateIndex][2]*SK_BETA[6] + P[stateIndex][6]*SK_BETA[3] - P[stateIndex][3]*SK_BETA[7] + P[stateIndex][22]*SK_BETA[1] - P[stateIndex][23]*SK_BETA[2]);
                 } else {
diff --git a/libraries/AP_NavEKF3/AP_NavEKF3_MagFusion.cpp b/libraries/AP_NavEKF3/AP_NavEKF3_MagFusion.cpp
index 51186a0103..0a53ab3add 100644
--- a/libraries/AP_NavEKF3/AP_NavEKF3_MagFusion.cpp
+++ b/libraries/AP_NavEKF3/AP_NavEKF3_MagFusion.cpp
@@ -602,7 +602,7 @@ void NavEKF3_core::FuseMagnetometer()
 
             if (!inhibitDelVelBiasStates) {
                 for (uint8_t index = 0; index < 3; index++) {
-                    uint8_t stateIndex = index + 13;
+                    const uint8_t stateIndex = index + 13;
                     if (!dvelBiasAxisInhibit[index]) {
                         Kfusion[stateIndex] = SK_MX[0]*(P[stateIndex][19] + P[stateIndex][1]*SH_MAG[0] - P[stateIndex][2]*SH_MAG[1] + P[stateIndex][3]*SH_MAG[2] + P[stateIndex][0]*SK_MX[2] - P[stateIndex][16]*SK_MX[1] + P[stateIndex][17]*SK_MX[4] - P[stateIndex][18]*SK_MX[3]);
                     } else {
@@ -682,7 +682,7 @@ void NavEKF3_core::FuseMagnetometer()
 
             if (!inhibitDelVelBiasStates) {
                 for (uint8_t index = 0; index < 3; index++) {
-                    uint8_t stateIndex = index + 13;
+                    const uint8_t stateIndex = index + 13;
                     if (!dvelBiasAxisInhibit[index]) {
                         Kfusion[stateIndex] = SK_MY[0]*(P[stateIndex][20] + P[stateIndex][0]*SH_MAG[2] + P[stateIndex][1]*SH_MAG[1] + P[stateIndex][2]*SH_MAG[0] - P[stateIndex][3]*SK_MY[2] - P[stateIndex][17]*SK_MY[1] - P[stateIndex][16]*SK_MY[3] + P[stateIndex][18]*SK_MY[4]);
                     } else {
@@ -764,7 +764,7 @@ void NavEKF3_core::FuseMagnetometer()
 
             if (!inhibitDelVelBiasStates) {
                 for (uint8_t index = 0; index < 3; index++) {
-                    uint8_t stateIndex = index + 13;
+                    const uint8_t stateIndex = index + 13;
                     if (!dvelBiasAxisInhibit[index]) {
                         Kfusion[stateIndex] = SK_MZ[0]*(P[stateIndex][21] + P[stateIndex][0]*SH_MAG[1] - P[stateIndex][1]*SH_MAG[2] + P[stateIndex][3]*SH_MAG[0] + P[stateIndex][2]*SK_MZ[2] + P[stateIndex][18]*SK_MZ[1] + P[stateIndex][16]*SK_MZ[4] - P[stateIndex][17]*SK_MZ[3]);
                     } else {
@@ -1302,7 +1302,7 @@ void NavEKF3_core::FuseDeclination(float declErr)
 
     if (!inhibitDelVelBiasStates) {
         for (uint8_t index = 0; index < 3; index++) {
-            uint8_t stateIndex = index + 13;
+            const uint8_t stateIndex = index + 13;
             if (!dvelBiasAxisInhibit[index]) {
                 Kfusion[stateIndex] = -t4*t13*(P[stateIndex][16]*magE-P[stateIndex][17]*magN);
             } else {
diff --git a/libraries/AP_NavEKF3/AP_NavEKF3_OptFlowFusion.cpp b/libraries/AP_NavEKF3/AP_NavEKF3_OptFlowFusion.cpp
index 8c55f8028a..fc8626a5bc 100644
--- a/libraries/AP_NavEKF3/AP_NavEKF3_OptFlowFusion.cpp
+++ b/libraries/AP_NavEKF3/AP_NavEKF3_OptFlowFusion.cpp
@@ -467,7 +467,7 @@ void NavEKF3_core::FuseOptFlow()
 
             if (!inhibitDelVelBiasStates) {
                 for (uint8_t index = 0; index < 3; index++) {
-                    uint8_t stateIndex = index + 13;
+                    const uint8_t stateIndex = index + 13;
                     if (!dvelBiasAxisInhibit[index]) {
                         Kfusion[stateIndex] = t78*(P[stateIndex][0]*t2*t5-P[stateIndex][4]*t2*t7+P[stateIndex][1]*t2*t15+P[stateIndex][6]*t2*t10+P[stateIndex][2]*t2*t19-P[stateIndex][3]*t2*t22+P[stateIndex][5]*t2*t27);
                     } else {
@@ -643,7 +643,7 @@ void NavEKF3_core::FuseOptFlow()
 
             if (!inhibitDelVelBiasStates) {
                 for (uint8_t index = 0; index < 3; index++) {
-                    uint8_t stateIndex = index + 13;
+                    const uint8_t stateIndex = index + 13;
                     if (!dvelBiasAxisInhibit[index]) {
                         Kfusion[stateIndex] = -t78*(P[stateIndex][0]*t2*t5+P[stateIndex][5]*t2*t8-P[stateIndex][6]*t2*t10+P[stateIndex][1]*t2*t16-P[stateIndex][2]*t2*t19+P[stateIndex][3]*t2*t22+P[stateIndex][4]*t2*t27);
                     } else {
diff --git a/libraries/AP_NavEKF3/AP_NavEKF3_PosVelFusion.cpp b/libraries/AP_NavEKF3/AP_NavEKF3_PosVelFusion.cpp
index ce79261c26..94b4dff55e 100644
--- a/libraries/AP_NavEKF3/AP_NavEKF3_PosVelFusion.cpp
+++ b/libraries/AP_NavEKF3/AP_NavEKF3_PosVelFusion.cpp
@@ -1388,7 +1388,7 @@ void NavEKF3_core::FuseBodyVel()
 
             if (!inhibitDelVelBiasStates) {
                 for (uint8_t index = 0; index < 3; index++) {
-                    uint8_t stateIndex = index + 13;
+                    const uint8_t stateIndex = index + 13;
                     if (!dvelBiasAxisInhibit[index]) {
                         Kfusion[stateIndex] = t77*(P[stateIndex][5]*t4+P[stateIndex][4]*t9+P[stateIndex][0]*t14-P[stateIndex][6]*t11+P[stateIndex][1]*t18-P[stateIndex][2]*t21+P[stateIndex][3]*t24);
                     } else {
@@ -1565,7 +1565,7 @@ void NavEKF3_core::FuseBodyVel()
 
             if (!inhibitDelVelBiasStates) {
                 for (uint8_t index = 0; index < 3; index++) {
-                    uint8_t stateIndex = index + 13;
+                    const uint8_t stateIndex = index + 13;
                     if (!dvelBiasAxisInhibit[index]) {
                         Kfusion[stateIndex] = t77*(-P[stateIndex][4]*t3+P[stateIndex][5]*t8+P[stateIndex][0]*t15+P[stateIndex][6]*t12+P[stateIndex][1]*t18+P[stateIndex][2]*t22-P[stateIndex][3]*t25);
                     } else {
@@ -1743,7 +1743,7 @@ void NavEKF3_core::FuseBodyVel()
 
             if (!inhibitDelVelBiasStates) {
                 for (uint8_t index = 0; index < 3; index++) {
-                    uint8_t stateIndex = index + 13;
+                    const uint8_t stateIndex = index + 13;
                     if (!dvelBiasAxisInhibit[index]) {
                         Kfusion[stateIndex] = t77*(P[stateIndex][4]*t4+P[stateIndex][0]*t14+P[stateIndex][6]*t9-P[stateIndex][5]*t11-P[stateIndex][1]*t17+P[stateIndex][2]*t20+P[stateIndex][3]*t24);
                     } else {
diff --git a/libraries/AP_NavEKF3/AP_NavEKF3_RngBcnFusion.cpp b/libraries/AP_NavEKF3/AP_NavEKF3_RngBcnFusion.cpp
index 4abc2ef5a2..bbc8a9d694 100644
--- a/libraries/AP_NavEKF3/AP_NavEKF3_RngBcnFusion.cpp
+++ b/libraries/AP_NavEKF3/AP_NavEKF3_RngBcnFusion.cpp
@@ -150,7 +150,7 @@ void NavEKF3_core::FuseRngBcn()
 
         if (!inhibitDelVelBiasStates) {
             for (uint8_t index = 0; index < 3; index++) {
-                uint8_t stateIndex = index + 13;
+                const uint8_t stateIndex = index + 13;
                 if (!dvelBiasAxisInhibit[index]) {
                     Kfusion[stateIndex] = -t26*(P[stateIndex][7]*t4*t9+P[stateIndex][8]*t3*t9+P[stateIndex][9]*t2*t9);
                 } else {
diff --git a/libraries/AP_NavEKF3/AP_NavEKF3_core.cpp b/libraries/AP_NavEKF3/AP_NavEKF3_core.cpp
index e341b8cd79..91e3f4a809 100644
--- a/libraries/AP_NavEKF3/AP_NavEKF3_core.cpp
+++ b/libraries/AP_NavEKF3/AP_NavEKF3_core.cpp
@@ -1683,7 +1683,7 @@ void NavEKF3_core::CovariancePrediction(Vector3f *rotVarVecPtr)
     // interacton with other states
     if (!inhibitDelVelBiasStates) {
         for (uint8_t index=0; index<3; index++) {
-            uint8_t stateIndex = index + 13;
+            const uint8_t stateIndex = index + 13;
             if (dvelBiasAxisInhibit[index]) {
                 zeroCols(nextP,stateIndex,stateIndex);
                 nextP[stateIndex][stateIndex] = dvelBiasAxisVarPrev[index];