diff --git a/ArduCopter/Attitude.pde b/ArduCopter/Attitude.pde
index 33957b17fd..a2306cb81a 100644
--- a/ArduCopter/Attitude.pde
+++ b/ArduCopter/Attitude.pde
@@ -82,7 +82,7 @@ static float get_look_ahead_yaw()
 static void update_thr_average()
 {
     // ensure throttle_average has been initialised
-    if( throttle_average == 0 ) {
+    if( AP_Math::is_zero(throttle_average) ) {
         throttle_average = g.throttle_mid;
         // update position controller
         pos_control.set_throttle_hover(throttle_average);
diff --git a/ArduCopter/GCS_Mavlink.pde b/ArduCopter/GCS_Mavlink.pde
index a059d481de..a31795fd6c 100644
--- a/ArduCopter/GCS_Mavlink.pde
+++ b/ArduCopter/GCS_Mavlink.pde
@@ -1053,7 +1053,7 @@ void GCS_MAVLINK::handleMessage(mavlink_message_t* msg)
 
             float takeoff_alt = packet.param7 * 100;      // Convert m to cm
 
-            if(do_user_takeoff(takeoff_alt, !packet.param3)) {
+            if(do_user_takeoff(takeoff_alt, AP_Math::is_zero(packet.param3))) {
                 result = MAV_RESULT_ACCEPTED;
             } else {
                 result = MAV_RESULT_FAILED;
@@ -1087,7 +1087,7 @@ void GCS_MAVLINK::handleMessage(mavlink_message_t* msg)
             // param4 : relative offset (1) or absolute angle (0)
             if ((packet.param1 >= 0.0f)   &&
             	(packet.param1 <= 360.0f) &&
-            	((packet.param4 == 0) || (packet.param4 == 1))) {
+            	(AP_Math::is_zero(packet.param4) || AP_Math::is_equal(packet.param4,1.0f))) {
             	set_auto_yaw_look_at_heading(packet.param1, packet.param2, (int8_t)packet.param3, (uint8_t)packet.param4);
                 result = MAV_RESULT_ACCEPTED;
             } else {
@@ -1114,7 +1114,7 @@ void GCS_MAVLINK::handleMessage(mavlink_message_t* msg)
             // param6 : longitude
             // param7 : altitude (absolute)
             result = MAV_RESULT_FAILED; // assume failure
-            if(packet.param1 == 1 || (packet.param5 == 0 && packet.param6 == 0 && packet.param7 == 0)) {
+            if(AP_Math::is_equal(packet.param1,1.0f) || AP_Math::is_zero(packet.param5) && AP_Math::is_zero(packet.param6) && AP_Math::is_zero(packet.param7)) {
                 if (set_home_to_current_location_and_lock()) {
                     result = MAV_RESULT_ACCEPTED;
                 }
@@ -1158,7 +1158,7 @@ void GCS_MAVLINK::handleMessage(mavlink_message_t* msg)
                 result = MAV_RESULT_FAILED;
                 break;
             }
-            if (packet.param1 == 1) {
+            if (AP_Math::is_equal(packet.param1,1.0f)) {
                 // gyro offset calibration
                 ins.init_gyro();
                 // reset ahrs gyro bias
@@ -1168,13 +1168,13 @@ void GCS_MAVLINK::handleMessage(mavlink_message_t* msg)
                 } else {
                     result = MAV_RESULT_FAILED;
                 }
-            } else if (packet.param3 == 1) {
+            } else if (AP_Math::is_equal(packet.param3,1.0f)) {
                 // fast barometer calibration
                 init_barometer(false);
                 result = MAV_RESULT_ACCEPTED;
-            } else if (packet.param4 == 1) {
+            } else if (AP_Math::is_equal(packet.param4,1.0f)) {
                 result = MAV_RESULT_UNSUPPORTED;
-            } else if (packet.param5 == 1) {
+            } else if (AP_Math::is_equal(packet.param5,1.0f)) {
                 // 3d accel calibration
                 float trim_roll, trim_pitch;
                 // this blocks
@@ -1186,19 +1186,19 @@ void GCS_MAVLINK::handleMessage(mavlink_message_t* msg)
                 } else {
                     result = MAV_RESULT_FAILED;
                 }
-            } else if (packet.param6 == 1) {
+            } else if (AP_Math::is_equal(packet.param6,1.0f)) {
                 // compassmot calibration
                 result = mavlink_compassmot(chan);
             }
             break;
 
         case MAV_CMD_PREFLIGHT_SET_SENSOR_OFFSETS:
-            if (packet.param1 == 2) {
+            if (AP_Math::is_equal(packet.param1,2.0f)) {
                 // save first compass's offsets
                 compass.set_and_save_offsets(0, packet.param2, packet.param3, packet.param4);
                 result = MAV_RESULT_ACCEPTED;
             }
-            if (packet.param1 == 5) {
+            if (AP_Math::is_equal(packet.param1,5.0f)) {
                 // save secondary compass's offsets
                 compass.set_and_save_offsets(1, packet.param2, packet.param3, packet.param4);
                 result = MAV_RESULT_ACCEPTED;
@@ -1206,12 +1206,12 @@ void GCS_MAVLINK::handleMessage(mavlink_message_t* msg)
             break;
 
         case MAV_CMD_COMPONENT_ARM_DISARM:
-            if (packet.param1 == 1.0f) {
+            if (AP_Math::is_equal(packet.param1,1.0f)) {
                 // attempt to arm and return success or failure
                 if (init_arm_motors(true)) {
                     result = MAV_RESULT_ACCEPTED;
                 }
-            } else if (packet.param1 == 0.0f && (mode_has_manual_throttle(control_mode) || ap.land_complete))  {
+            } else if (AP_Math::is_zero(packet.param1) && (mode_has_manual_throttle(control_mode) || ap.land_complete))  {
                 init_disarm_motors();
                 result = MAV_RESULT_ACCEPTED;
             } else {
@@ -1244,12 +1244,12 @@ void GCS_MAVLINK::handleMessage(mavlink_message_t* msg)
             break;
 
         case MAV_CMD_PREFLIGHT_REBOOT_SHUTDOWN:
-            if (packet.param1 == 1 || packet.param1 == 3) {
+            if (AP_Math::is_equal(packet.param1,1.0f) || AP_Math::is_equal(packet.param1,3.0f)) {
                 AP_Notify::events.firmware_update = 1;
                 update_notify();
                 hal.scheduler->delay(50);
                 // when packet.param1 == 3 we reboot to hold in bootloader
-                hal.scheduler->reboot(packet.param1 == 3);
+                hal.scheduler->reboot(AP_Math::is_equal(packet.param1,3.0f));
                 result = MAV_RESULT_ACCEPTED;
             }
             break;
@@ -1329,7 +1329,7 @@ void GCS_MAVLINK::handleMessage(mavlink_message_t* msg)
 #endif
 
         case MAV_CMD_REQUEST_AUTOPILOT_CAPABILITIES: {
-            if (packet.param1 == 1) {
+            if (AP_Math::is_equal(packet.param1,1.0f)) {
                 gcs[chan-MAVLINK_COMM_0].send_autopilot_version();
                 result = MAV_RESULT_ACCEPTED;
             }
@@ -1481,9 +1481,9 @@ void GCS_MAVLINK::handleMessage(mavlink_message_t* msg)
 
         // m/s/s
         Vector3f accels;
-        accels.x = packet.xacc * (GRAVITY_MSS/1000.0);
-        accels.y = packet.yacc * (GRAVITY_MSS/1000.0);
-        accels.z = packet.zacc * (GRAVITY_MSS/1000.0);
+        accels.x = packet.xacc * (GRAVITY_MSS/1000.0f);
+        accels.y = packet.yacc * (GRAVITY_MSS/1000.0f);
+        accels.z = packet.zacc * (GRAVITY_MSS/1000.0f);
 
         ins.set_gyro(0, gyros);
 
diff --git a/ArduCopter/commands_logic.pde b/ArduCopter/commands_logic.pde
index f787cd9eb9..271f0faf60 100644
--- a/ArduCopter/commands_logic.pde
+++ b/ArduCopter/commands_logic.pde
@@ -684,7 +684,7 @@ static bool verify_circle(const AP_Mission::Mission_Command& cmd)
             Vector3f circle_center = pv_location_to_vector(cmd.content.location);
 
             // set target altitude if not provided
-            if (circle_center.z == 0) {
+            if (AP_Math::is_zero(circle_center.z)) {
                 circle_center.z = curr_pos.z;
             }
 
diff --git a/ArduCopter/control_auto.pde b/ArduCopter/control_auto.pde
index 23bf030dde..386510eac2 100644
--- a/ArduCopter/control_auto.pde
+++ b/ArduCopter/control_auto.pde
@@ -171,7 +171,7 @@ static void auto_wp_run()
     if (!failsafe.radio) {
         // get pilot's desired yaw rate
         target_yaw_rate = get_pilot_desired_yaw_rate(g.rc_4.control_in);
-        if (target_yaw_rate != 0) {
+        if (!AP_Math::is_zero(target_yaw_rate)) {
             set_auto_yaw_mode(AUTO_YAW_HOLD);
         }
     }
@@ -227,7 +227,7 @@ static void auto_spline_run()
     if (!failsafe.radio) {
         // get pilot's desired yaw rate
         target_yaw_rate = get_pilot_desired_yaw_rate(g.rc_4.control_in);
-        if (target_yaw_rate != 0) {
+        if (!AP_Math::is_zero(target_yaw_rate)) {
             set_auto_yaw_mode(AUTO_YAW_HOLD);
         }
     }
@@ -550,7 +550,7 @@ static void set_auto_yaw_look_at_heading(float angle_deg, float turn_rate_dps, i
     }
 
     // get turn speed
-    if (turn_rate_dps == 0 ) {
+    if (AP_Math::is_zero(turn_rate_dps)) {
         // default to regular auto slew rate
         yaw_look_at_heading_slew = AUTO_YAW_SLEW_RATE;
     }else{
diff --git a/ArduCopter/control_autotune.pde b/ArduCopter/control_autotune.pde
index 722fc36a04..424c432765 100644
--- a/ArduCopter/control_autotune.pde
+++ b/ArduCopter/control_autotune.pde
@@ -295,7 +295,7 @@ static void autotune_run()
         pos_control.set_alt_target_to_current_alt();
     }else{
         // check if pilot is overriding the controls
-        if (target_roll != 0 || target_pitch != 0 || target_yaw_rate != 0.0f || target_climb_rate != 0) {
+        if (!AP_Math::is_zero(target_roll) || !AP_Math::is_zero(target_pitch) || !AP_Math::is_zero(target_yaw_rate) || !AP_Math::is_zero(target_climb_rate)) {
             if (!autotune_state.pilot_override) {
                 autotune_state.pilot_override = true;
                 // set gains to their original values
@@ -334,7 +334,7 @@ static void autotune_attitude_control()
 {
     float rotation_rate = 0.0f;        // rotation rate in radians/second
     float lean_angle = 0.0f;
-    const float direction_sign = autotune_state.positive_direction ? 1.0 : -1.0;
+    const float direction_sign = autotune_state.positive_direction ? 1.0f : -1.0f;
 
     // check tuning step
     switch (autotune_state.step) {
@@ -747,7 +747,7 @@ static void autotune_backup_gains_and_initialise()
 
     autotune_desired_yaw = ahrs.yaw_sensor;
 
-    g.autotune_aggressiveness = constrain_float(g.autotune_aggressiveness, 0.05, 0.1);
+    g.autotune_aggressiveness = constrain_float(g.autotune_aggressiveness, 0.05f, 0.1f);
 
     // backup original pids and initialise tuned pid values
     if (autotune_roll_enabled()) {
@@ -789,7 +789,7 @@ static void autotune_load_orig_gains()
     // sanity check the gains
     bool failed = false;
     if (autotune_roll_enabled()) {
-        if ((orig_roll_rp != 0) || (orig_roll_sp != 0)) {
+        if (!AP_Math::is_zero(orig_roll_rp) || !AP_Math::is_zero(orig_roll_sp)) {
             g.pid_rate_roll.kP(orig_roll_rp);
             g.pid_rate_roll.kI(orig_roll_ri);
             g.pid_rate_roll.kD(orig_roll_rd);
@@ -799,7 +799,7 @@ static void autotune_load_orig_gains()
         }
     }
     if (autotune_pitch_enabled()) {
-        if ((orig_pitch_rp != 0) || (orig_pitch_sp != 0)) {
+        if (!AP_Math::is_zero(orig_pitch_rp) || !AP_Math::is_zero(orig_pitch_sp)) {
             g.pid_rate_pitch.kP(orig_pitch_rp);
             g.pid_rate_pitch.kI(orig_pitch_ri);
             g.pid_rate_pitch.kD(orig_pitch_rd);
@@ -809,7 +809,7 @@ static void autotune_load_orig_gains()
         }
     }
     if (autotune_yaw_enabled()) {
-        if ((orig_yaw_rp != 0) || (orig_yaw_sp != 0) || (orig_yaw_rLPF != 0)) {
+        if (!AP_Math::is_zero(orig_yaw_rp) || !AP_Math::is_zero(orig_yaw_sp) || !AP_Math::is_zero(orig_yaw_rLPF)) {
             g.pid_rate_yaw.kP(orig_yaw_rp);
             g.pid_rate_yaw.kI(orig_yaw_ri);
             g.pid_rate_yaw.kD(orig_yaw_rd);
@@ -831,7 +831,7 @@ static void autotune_load_tuned_gains()
     // sanity check the gains
     bool failed = true;
     if (autotune_roll_enabled()) {
-        if (tune_roll_rp != 0) {
+        if (!AP_Math::is_zero(tune_roll_rp)) {
             g.pid_rate_roll.kP(tune_roll_rp);
             g.pid_rate_roll.kI(tune_roll_rp*AUTOTUNE_PI_RATIO_FINAL);
             g.pid_rate_roll.kD(tune_roll_rd);
@@ -840,7 +840,7 @@ static void autotune_load_tuned_gains()
         }
     }
     if (autotune_pitch_enabled()) {
-        if (tune_pitch_rp != 0) {
+        if (!AP_Math::is_zero(tune_pitch_rp)) {
             g.pid_rate_pitch.kP(tune_pitch_rp);
             g.pid_rate_pitch.kI(tune_pitch_rp*AUTOTUNE_PI_RATIO_FINAL);
             g.pid_rate_pitch.kD(tune_pitch_rd);
@@ -849,7 +849,7 @@ static void autotune_load_tuned_gains()
         }
     }
     if (autotune_yaw_enabled()) {
-        if (tune_yaw_rp != 0) {
+        if (!AP_Math::is_zero(tune_yaw_rp)) {
             g.pid_rate_yaw.kP(tune_yaw_rp);
             g.pid_rate_yaw.kI(tune_yaw_rp*AUTOTUNE_YAW_PI_RATIO_FINAL);
             g.pid_rate_yaw.kD(0.0f);
@@ -871,21 +871,21 @@ static void autotune_load_intra_test_gains()
     // we are restarting tuning so reset gains to tuning-start gains (i.e. low I term)
     // sanity check the gains
     bool failed = true;
-    if (autotune_roll_enabled() && (orig_roll_rp != 0)) {
+    if (autotune_roll_enabled() && !AP_Math::is_zero(orig_roll_rp)) {
         g.pid_rate_roll.kP(orig_roll_rp);
         g.pid_rate_roll.kI(orig_roll_rp*AUTOTUNE_PI_RATIO_FOR_TESTING);
         g.pid_rate_roll.kD(orig_roll_rd);
         g.p_stabilize_roll.kP(orig_roll_sp);
         failed = false;
     }
-    if (autotune_pitch_enabled() && (orig_pitch_rp != 0)) {
+    if (autotune_pitch_enabled() && !AP_Math::is_zero(orig_pitch_rp)) {
         g.pid_rate_pitch.kP(orig_pitch_rp);
         g.pid_rate_pitch.kI(orig_pitch_rp*AUTOTUNE_PI_RATIO_FOR_TESTING);
         g.pid_rate_pitch.kD(orig_pitch_rd);
         g.p_stabilize_pitch.kP(orig_pitch_sp);
         failed = false;
     }
-    if (autotune_yaw_enabled() && (orig_yaw_rp != 0)) {
+    if (autotune_yaw_enabled() && !AP_Math::is_zero(orig_yaw_rp)) {
         g.pid_rate_yaw.kP(orig_yaw_rp);
         g.pid_rate_yaw.kI(orig_yaw_rp*AUTOTUNE_PI_RATIO_FOR_TESTING);
         g.pid_rate_yaw.kD(orig_yaw_rd);
@@ -906,7 +906,7 @@ static void autotune_load_twitch_gains()
     bool failed = true;
     switch (autotune_state.axis) {
         case AUTOTUNE_AXIS_ROLL:
-            if (tune_roll_rp != 0) {
+            if (!AP_Math::is_zero(tune_roll_rp)) {
                 g.pid_rate_roll.kP(tune_roll_rp);
                 g.pid_rate_roll.kI(tune_roll_rp*0.01f);
                 g.pid_rate_roll.kD(tune_roll_rd);
@@ -915,7 +915,7 @@ static void autotune_load_twitch_gains()
             }
             break;
         case AUTOTUNE_AXIS_PITCH:
-            if (tune_pitch_rp != 0) {
+            if (!AP_Math::is_zero(tune_pitch_rp)) {
                 g.pid_rate_pitch.kP(tune_pitch_rp);
                 g.pid_rate_pitch.kI(tune_pitch_rp*0.01f);
                 g.pid_rate_pitch.kD(tune_pitch_rd);
@@ -924,7 +924,7 @@ static void autotune_load_twitch_gains()
             }
             break;
         case AUTOTUNE_AXIS_YAW:
-            if (tune_yaw_rp != 0) {
+            if (!AP_Math::is_zero(tune_yaw_rp)) {
                 g.pid_rate_yaw.kP(tune_yaw_rp);
                 g.pid_rate_yaw.kI(tune_yaw_rp*0.01f);
                 g.pid_rate_yaw.kD(0.0f);
@@ -947,7 +947,7 @@ static void autotune_save_tuning_gains()
     // if we successfully completed tuning
     if (autotune_state.mode == AUTOTUNE_MODE_SUCCESS) {
         // sanity check the rate P values
-        if (autotune_roll_enabled() && (tune_roll_rp != 0)) {
+        if (autotune_roll_enabled() && !AP_Math::is_zero(tune_roll_rp)) {
             // rate roll gains
             g.pid_rate_roll.kP(tune_roll_rp);
             g.pid_rate_roll.kI(tune_roll_rp*AUTOTUNE_PI_RATIO_FINAL);
@@ -968,7 +968,7 @@ static void autotune_save_tuning_gains()
             orig_roll_sp = g.p_stabilize_roll.kP();
         }
 
-        if (autotune_pitch_enabled() && (tune_pitch_rp != 0)) {
+        if (autotune_pitch_enabled() && !AP_Math::is_zero(tune_pitch_rp)) {
             // rate pitch gains
             g.pid_rate_pitch.kP(tune_pitch_rp);
             g.pid_rate_pitch.kI(tune_pitch_rp*AUTOTUNE_PI_RATIO_FINAL);
@@ -989,7 +989,7 @@ static void autotune_save_tuning_gains()
             orig_pitch_sp = g.p_stabilize_pitch.kP();
         }
 
-        if (autotune_yaw_enabled() && (tune_yaw_rp != 0)) {
+        if (autotune_yaw_enabled() && !AP_Math::is_zero(tune_yaw_rp)) {
             // rate yaw gains
             g.pid_rate_yaw.kP(tune_yaw_rp);
             g.pid_rate_yaw.kI(tune_yaw_rp*AUTOTUNE_YAW_PI_RATIO_FINAL);
diff --git a/ArduCopter/control_circle.pde b/ArduCopter/control_circle.pde
index 34acc19e07..9e6b21f204 100644
--- a/ArduCopter/control_circle.pde
+++ b/ArduCopter/control_circle.pde
@@ -44,7 +44,7 @@ static void circle_run()
     if (!failsafe.radio) {
         // get pilot's desired yaw rate
         target_yaw_rate = get_pilot_desired_yaw_rate(g.rc_4.control_in);
-        if (target_yaw_rate != 0) {
+        if (!AP_Math::is_zero(target_yaw_rate)) {
             circle_pilot_yaw_override = true;
         }
 
diff --git a/ArduCopter/control_drift.pde b/ArduCopter/control_drift.pde
index fc3d85ed1f..a64f66c9c3 100644
--- a/ArduCopter/control_drift.pde
+++ b/ArduCopter/control_drift.pde
@@ -82,7 +82,7 @@ static void drift_run()
     target_roll = constrain_int16(target_roll, -4500, 4500);
 
     // If we let go of sticks, bring us to a stop
-    if(target_pitch == 0){
+    if(AP_Math::is_zero(target_pitch)){
         // .14/ (.03 * 100) = 4.6 seconds till full breaking
         breaker += .03f;
         breaker = min(breaker, DRIFT_SPEEDGAIN);
diff --git a/ArduCopter/control_guided.pde b/ArduCopter/control_guided.pde
index fa1f7c295a..bed67bf565 100644
--- a/ArduCopter/control_guided.pde
+++ b/ArduCopter/control_guided.pde
@@ -232,7 +232,7 @@ static void guided_pos_control_run()
     if (!failsafe.radio) {
         // get pilot's desired yaw rate
         target_yaw_rate = get_pilot_desired_yaw_rate(g.rc_4.control_in);
-        if (target_yaw_rate != 0) {
+        if (!AP_Math::is_zero(target_yaw_rate)) {
             set_auto_yaw_mode(AUTO_YAW_HOLD);
         }
     }
@@ -262,7 +262,7 @@ static void guided_vel_control_run()
     if (!failsafe.radio) {
         // get pilot's desired yaw rate
         target_yaw_rate = get_pilot_desired_yaw_rate(g.rc_4.control_in);
-        if (target_yaw_rate != 0) {
+        if (!AP_Math::is_zero(target_yaw_rate)) {
             set_auto_yaw_mode(AUTO_YAW_HOLD);
         }
     }
@@ -301,7 +301,7 @@ static void guided_posvel_control_run()
     if (!failsafe.radio) {
         // get pilot's desired yaw rate
         target_yaw_rate = get_pilot_desired_yaw_rate(g.rc_4.control_in);
-        if (target_yaw_rate != 0) {
+        if (!AP_Math::is_zero(target_yaw_rate)) {
             set_auto_yaw_mode(AUTO_YAW_HOLD);
         }
     }
@@ -389,12 +389,12 @@ static bool guided_limit_check()
     const Vector3f& curr_pos = inertial_nav.get_position();
 
     // check if we have gone below min alt
-    if ((guided_limit.alt_min_cm != 0.0f) && (curr_pos.z < guided_limit.alt_min_cm)) {
+    if (!AP_Math::is_zero(guided_limit.alt_min_cm) && (curr_pos.z < guided_limit.alt_min_cm)) {
         return true;
     }
 
     // check if we have gone above max alt
-    if ((guided_limit.alt_max_cm != 0.0f) && (curr_pos.z > guided_limit.alt_max_cm)) {
+    if (!AP_Math::is_zero(guided_limit.alt_max_cm) && (curr_pos.z > guided_limit.alt_max_cm)) {
         return true;
     }
 
diff --git a/ArduCopter/control_poshold.pde b/ArduCopter/control_poshold.pde
index 5f6c81a74e..cd97c0531a 100644
--- a/ArduCopter/control_poshold.pde
+++ b/ArduCopter/control_poshold.pde
@@ -228,7 +228,7 @@ static void poshold_run()
                 poshold_update_pilot_lean_angle(poshold.pilot_roll, target_roll);
 
                 // switch to BRAKE mode for next iteration if no pilot input
-                if ((target_roll == 0) && (abs(poshold.pilot_roll) < 2 * g.poshold_brake_rate)) {
+                if (AP_Math::is_zero(target_roll) && (abs(poshold.pilot_roll) < 2 * g.poshold_brake_rate)) {
                     // initialise BRAKE mode
                     poshold.roll_mode = POSHOLD_BRAKE;        // Set brake roll mode
                     poshold.brake_roll = 0;                  // initialise braking angle to zero
@@ -277,7 +277,7 @@ static void poshold_run()
                 poshold.roll = poshold.brake_roll + poshold.wind_comp_roll;
 
                 // check for pilot input
-                if (target_roll != 0) {
+                if (!AP_Math::is_zero(target_roll)) {
                     // init transition to pilot override
                     poshold_roll_controller_to_pilot_override();
                 }
@@ -322,7 +322,7 @@ static void poshold_run()
                 poshold_update_pilot_lean_angle(poshold.pilot_pitch, target_pitch);
 
                 // switch to BRAKE mode for next iteration if no pilot input
-                if ((target_pitch == 0) && (abs(poshold.pilot_pitch) < 2 * g.poshold_brake_rate)) {
+                if (AP_Math::is_zero(target_pitch) && (abs(poshold.pilot_pitch) < 2 * g.poshold_brake_rate)) {
                     // initialise BRAKE mode
                     poshold.pitch_mode = POSHOLD_BRAKE;       // set brake pitch mode
                     poshold.brake_pitch = 0;                 // initialise braking angle to zero
@@ -371,7 +371,7 @@ static void poshold_run()
                 poshold.pitch = poshold.brake_pitch + poshold.wind_comp_pitch;
 
                 // check for pilot input
-                if (target_pitch != 0) {
+                if (!AP_Math::is_zero(target_pitch)) {
                     // init transition to pilot override
                     poshold_pitch_controller_to_pilot_override();
                 }
@@ -453,9 +453,9 @@ static void poshold_run()
                     poshold.pitch = poshold_mix_controls(brake_to_loiter_mix, poshold.brake_pitch + poshold.wind_comp_pitch, wp_nav.get_pitch());
 
                     // check for pilot input
-                    if (target_roll != 0 || target_pitch != 0) {
+                    if (!AP_Math::is_zero(target_roll) || !AP_Math::is_zero(target_pitch)) {
                         // if roll input switch to pilot override for roll
-                        if (target_roll != 0) {
+                        if (!AP_Math::is_zero(target_roll)) {
                             // init transition to pilot override
                             poshold_roll_controller_to_pilot_override();
                             // switch pitch-mode to brake (but ready to go back to loiter anytime)
@@ -463,10 +463,10 @@ static void poshold_run()
                             poshold.pitch_mode = POSHOLD_BRAKE_READY_TO_LOITER;
                         }
                         // if pitch input switch to pilot override for pitch
-                        if (target_pitch != 0) {
+                        if (!AP_Math::is_zero(target_pitch)) {
                             // init transition to pilot override
                             poshold_pitch_controller_to_pilot_override();
-                            if (target_roll == 0) {
+                            if (AP_Math::is_zero(target_roll)) {
                                 // switch roll-mode to brake (but ready to go back to loiter anytime)
                                 // no need to reset poshold.brake_roll here as wind comp has not been updated since last brake_roll computation
                                 poshold.roll_mode = POSHOLD_BRAKE_READY_TO_LOITER;
@@ -487,9 +487,9 @@ static void poshold_run()
                     poshold_update_wind_comp_estimate();
 
                     // check for pilot input
-                    if (target_roll != 0 || target_pitch != 0) {
+                    if (!AP_Math::is_zero(target_roll) || !AP_Math::is_zero(target_pitch)) {
                         // if roll input switch to pilot override for roll
-                        if (target_roll != 0) {
+                        if (!AP_Math::is_zero(target_roll)) {
                             // init transition to pilot override
                             poshold_roll_controller_to_pilot_override();
                             // switch pitch-mode to brake (but ready to go back to loiter anytime)
@@ -498,11 +498,11 @@ static void poshold_run()
                             poshold.brake_pitch = 0;
                         }
                         // if pitch input switch to pilot override for pitch
-                        if (target_pitch != 0) {
+                        if (!AP_Math::is_zero(target_pitch)) {
                             // init transition to pilot override
                             poshold_pitch_controller_to_pilot_override();
                             // if roll not overriden switch roll-mode to brake (but be ready to go back to loiter any time)
-                            if (target_roll == 0) {
+                            if (AP_Math::is_zero(target_roll)) {
                                 poshold.roll_mode = POSHOLD_BRAKE_READY_TO_LOITER;
                                 poshold.brake_roll = 0;
                             }
@@ -613,14 +613,14 @@ static void poshold_update_wind_comp_estimate()
     const Vector3f& accel_target = pos_control.get_accel_target();
 
     // update wind compensation in earth-frame lean angles
-    if (poshold.wind_comp_ef.x == 0) {
+    if (AP_Math::is_zero(poshold.wind_comp_ef.x)) {
         // if wind compensation has not been initialised set it immediately to the pos controller's desired accel in north direction
         poshold.wind_comp_ef.x = accel_target.x;
     } else {
         // low pass filter the position controller's lean angle output
         poshold.wind_comp_ef.x = (1.0f-TC_WIND_COMP)*poshold.wind_comp_ef.x + TC_WIND_COMP*accel_target.x;
     }
-    if (poshold.wind_comp_ef.y == 0) {
+    if (AP_Math::is_zero(poshold.wind_comp_ef.y)) {
         // if wind compensation has not been initialised set it immediately to the pos controller's desired accel in north direction
         poshold.wind_comp_ef.y = accel_target.y;
     } else {
diff --git a/ArduCopter/control_rtl.pde b/ArduCopter/control_rtl.pde
index 40b695b501..5b69c73259 100644
--- a/ArduCopter/control_rtl.pde
+++ b/ArduCopter/control_rtl.pde
@@ -144,7 +144,7 @@ static void rtl_climb_return_run()
     if (!failsafe.radio) {
         // get pilot's desired yaw rate
         target_yaw_rate = get_pilot_desired_yaw_rate(g.rc_4.control_in);
-        if (target_yaw_rate != 0) {
+        if (!AP_Math::is_zero(target_yaw_rate)) {
             set_auto_yaw_mode(AUTO_YAW_HOLD);
         }
     }
@@ -200,7 +200,7 @@ static void rtl_loiterathome_run()
     if (!failsafe.radio) {
         // get pilot's desired yaw rate
         target_yaw_rate = get_pilot_desired_yaw_rate(g.rc_4.control_in);
-        if (target_yaw_rate != 0) {
+        if (!AP_Math::is_zero(target_yaw_rate)) {
             set_auto_yaw_mode(AUTO_YAW_HOLD);
         }
     }
@@ -294,7 +294,7 @@ static void rtl_descent_run()
     attitude_control.angle_ef_roll_pitch_rate_ef_yaw(wp_nav.get_roll(), wp_nav.get_pitch(), target_yaw_rate);
 
     // check if we've reached within 20cm of final altitude
-    rtl_state_complete = fabs(pv_alt_above_origin(g.rtl_alt_final) - inertial_nav.get_altitude()) < 20.0f;
+    rtl_state_complete = fabsf(pv_alt_above_origin(g.rtl_alt_final) - inertial_nav.get_altitude()) < 20.0f;
 }
 
 // rtl_loiterathome_start - initialise controllers to loiter over home