diff --git a/src/main/common/maths.c b/src/main/common/maths.c
index 716d83e491..5ed16f916d 100644
--- a/src/main/common/maths.c
+++ b/src/main/common/maths.c
@@ -92,3 +92,52 @@ int scaleRange(int x, int srcMin, int srcMax, int destMin, int destMax) {
     return ((a / b) - (destMax - destMin)) + destMax;
 }
 
+// Normalize a vector
+void normalizeV(struct fp_vector *src, struct fp_vector *dest)
+{
+    float length;
+
+    length = sqrtf(src->X * src->X + src->Y * src->Y + src->Z * src->Z);
+    if (length != 0) {
+        dest->X = src->X / length;
+        dest->Y = src->Y / length;
+        dest->Z = src->Z / length;
+    }
+}
+
+// Rotate a vector *v by the euler angles defined by the 3-vector *delta.
+void rotateV(struct fp_vector *v, fp_angles_t *delta)
+{
+    struct fp_vector v_tmp = *v;
+
+    float mat[3][3];
+    float cosx, sinx, cosy, siny, cosz, sinz;
+    float coszcosx, sinzcosx, coszsinx, sinzsinx;
+
+    cosx = cosf(delta->angles.roll);
+    sinx = sinf(delta->angles.roll);
+    cosy = cosf(delta->angles.pitch);
+    siny = sinf(delta->angles.pitch);
+    cosz = cosf(delta->angles.yaw);
+    sinz = sinf(delta->angles.yaw);
+
+    coszcosx = cosz * cosx;
+    sinzcosx = sinz * cosx;
+    coszsinx = sinx * cosz;
+    sinzsinx = sinx * sinz;
+
+    mat[0][0] = cosz * cosy;
+    mat[0][1] = -cosy * sinz;
+    mat[0][2] = siny;
+    mat[1][0] = sinzcosx + (coszsinx * siny);
+    mat[1][1] = coszcosx - (sinzsinx * siny);
+    mat[1][2] = -sinx * cosy;
+    mat[2][0] = (sinzsinx) - (coszcosx * siny);
+    mat[2][1] = (coszsinx) + (sinzcosx * siny);
+    mat[2][2] = cosy * cosx;
+
+    v->X = v_tmp.X * mat[0][0] + v_tmp.Y * mat[1][0] + v_tmp.Z * mat[2][0];
+    v->Y = v_tmp.X * mat[0][1] + v_tmp.Y * mat[1][1] + v_tmp.Z * mat[2][1];
+    v->Z = v_tmp.X * mat[0][2] + v_tmp.Y * mat[1][2] + v_tmp.Z * mat[2][2];
+}
+
diff --git a/src/main/common/maths.h b/src/main/common/maths.h
index 85b08c6410..d65b87df22 100644
--- a/src/main/common/maths.h
+++ b/src/main/common/maths.h
@@ -21,16 +21,10 @@
 #define sq(x) ((x)*(x))
 #endif
 
-#ifdef M_PI
-// M_PI should be float, but previous definition may be double
-# undef M_PI
-#endif
-#define M_PI       3.14159265358979323846f
+// Use floating point M_PI instead explicitly.
+#define M_PIf       3.14159265358979323846f
 
-#define RADX10 (M_PI / 1800.0f)                  // 0.001745329252f
-#define RAD    (M_PI / 180.0f)
-
-#define DEG2RAD(degrees) (degrees * RAD)
+#define RAD    (M_PIf / 180.0f)
 
 #define min(a, b) ((a) < (b) ? (a) : (b))
 #define max(a, b) ((a) > (b) ? (a) : (b))
@@ -42,6 +36,31 @@ typedef struct stdev_t
     int m_n;
 } stdev_t;
 
+// Floating point 3 vector.
+typedef struct fp_vector {
+    float X;
+    float Y;
+    float Z;
+} t_fp_vector_def;
+
+typedef union {
+    float A[3];
+    t_fp_vector_def V;
+} t_fp_vector;
+
+// Floating point Euler angles.
+// Be carefull, could be either of degrees or radians.
+typedef struct fp_angles {
+    float roll;
+    float pitch;
+    float yaw;
+} fp_angles_def;
+
+typedef union {
+    float raw[3];
+    fp_angles_def angles;
+} fp_angles_t;
+
 int32_t applyDeadband(int32_t value, int32_t deadband);
 
 int constrain(int amt, int low, int high);
@@ -54,3 +73,7 @@ float devStandardDeviation(stdev_t *dev);
 float degreesToRadians(int16_t degrees);
 
 int scaleRange(int x, int srcMin, int srcMax, int destMin, int destMax);
+
+void normalizeV(struct fp_vector *src, struct fp_vector *dest);
+
+void rotateV(struct fp_vector *v, fp_angles_t *delta);
diff --git a/src/main/config/config.c b/src/main/config/config.c
index f582a8efd5..17c656ddd9 100644
--- a/src/main/config/config.c
+++ b/src/main/config/config.c
@@ -613,7 +613,7 @@ void activateConfig(void)
     imuRuntimeConfig.acc_unarmedcal = currentProfile->acc_unarmedcal;;
     imuRuntimeConfig.small_angle = masterConfig.small_angle;
 
-    configureImu(
+    configureIMU(
         &imuRuntimeConfig,
         &currentProfile->pidProfile,
         &currentProfile->accDeadband
diff --git a/src/main/drivers/accgyro_spi_mpu6000.c b/src/main/drivers/accgyro_spi_mpu6000.c
index 590e6e922a..8795bc54da 100644
--- a/src/main/drivers/accgyro_spi_mpu6000.c
+++ b/src/main/drivers/accgyro_spi_mpu6000.c
@@ -319,7 +319,7 @@ bool mpu6000SpiGyroDetect(gyro_t *gyro, uint16_t lpf)
     gyro->read = mpu6000SpiGyroRead;
     // 16.4 dps/lsb scalefactor
     gyro->scale = 1.0f / 16.4f;
-    //gyro->scale = (4.0f / 16.4f) * (M_PI / 180.0f) * 0.000001f;
+    //gyro->scale = (4.0f / 16.4f) * (M_PIf / 180.0f) * 0.000001f;
     delay(100);
     return true;
 }
diff --git a/src/main/drivers/accgyro_spi_mpu6500.c b/src/main/drivers/accgyro_spi_mpu6500.c
index 123ac08c35..7b3893cc1d 100644
--- a/src/main/drivers/accgyro_spi_mpu6500.c
+++ b/src/main/drivers/accgyro_spi_mpu6500.c
@@ -128,7 +128,7 @@ bool mpu6500SpiGyroDetect(gyro_t *gyro, uint16_t lpf)
 
     // 16.4 dps/lsb scalefactor
     gyro->scale = 1.0f / 16.4f;
-    //gyro->scale = (4.0f / 16.4f) * (M_PI / 180.0f) * 0.000001f;
+    //gyro->scale = (4.0f / 16.4f) * (M_PIf / 180.0f) * 0.000001f;
 
     // default lpf is 42Hz
     if (lpf >= 188)
diff --git a/src/main/flight/flight.h b/src/main/flight/flight.h
index ed96b43b1b..95877badf2 100644
--- a/src/main/flight/flight.h
+++ b/src/main/flight/flight.h
@@ -61,28 +61,6 @@ typedef enum {
 
 #define FLIGHT_DYNAMICS_INDEX_COUNT 3
 
-typedef struct fp_vector {
-    float X;
-    float Y;
-    float Z;
-} t_fp_vector_def;
-
-typedef union {
-    float A[3];
-    t_fp_vector_def V;
-} t_fp_vector;
-
-typedef struct fp_angles {
-    float roll;
-    float pitch;
-    float yaw;
-} fp_angles_def;
-
-typedef union {
-    float raw[3];
-    fp_angles_def angles;
-} fp_angles_t;
-
 typedef struct int16_flightDynamicsTrims_s {
     int16_t roll;
     int16_t pitch;
diff --git a/src/main/flight/imu.c b/src/main/flight/imu.c
index a9eb8b0de5..f0a4535a00 100644
--- a/src/main/flight/imu.c
+++ b/src/main/flight/imu.c
@@ -79,28 +79,28 @@ imuRuntimeConfig_t *imuRuntimeConfig;
 pidProfile_t *pidProfile;
 accDeadband_t *accDeadband;
 
-void configureImu(imuRuntimeConfig_t *initialImuRuntimeConfig, pidProfile_t *initialPidProfile, accDeadband_t *initialAccDeadband)
+void configureIMU(imuRuntimeConfig_t *initialImuRuntimeConfig, pidProfile_t *initialPidProfile, accDeadband_t *initialAccDeadband)
 {
     imuRuntimeConfig = initialImuRuntimeConfig;
     pidProfile = initialPidProfile;
     accDeadband = initialAccDeadband;
 }
 
-void imuInit()
+void initIMU()
 {
-    smallAngle = lrintf(acc_1G * cosf(RAD * imuRuntimeConfig->small_angle));
+    smallAngle = lrintf(acc_1G * cosf(degreesToRadians(imuRuntimeConfig->small_angle)));
     accVelScale = 9.80665f / acc_1G / 10000.0f;
-    gyroScaleRad = gyro.scale * (M_PI / 180.0f) * 0.000001f;
+    gyroScaleRad = gyro.scale * (M_PIf / 180.0f) * 0.000001f;
 }
 
 void calculateThrottleAngleScale(uint16_t throttle_correction_angle)
 {
-    throttleAngleScale = (1800.0f / M_PI) * (900.0f / throttle_correction_angle);
+    throttleAngleScale = (1800.0f / M_PIf) * (900.0f / throttle_correction_angle);
 }
 
 void calculateAccZLowPassFilterRCTimeConstant(float accz_lpf_cutoff)
 {
-    fc_acc = 0.5f / (M_PI * accz_lpf_cutoff); // calculate RC time constant used in the accZ lpf
+    fc_acc = 0.5f / (M_PIf * accz_lpf_cutoff); // calculate RC time constant used in the accZ lpf
 }
 
 void computeIMU(rollAndPitchTrims_t *accelerometerTrims, uint8_t mixerMode)
@@ -145,56 +145,6 @@ void computeIMU(rollAndPitchTrims_t *accelerometerTrims, uint8_t mixerMode)
 
 t_fp_vector EstG;
 
-// Normalize a vector
-void normalizeV(struct fp_vector *src, struct fp_vector *dest)
-{
-    float length;
-
-    length = sqrtf(src->X * src->X + src->Y * src->Y + src->Z * src->Z);
-    if (length != 0) {
-        dest->X = src->X / length;
-        dest->Y = src->Y / length;
-        dest->Z = src->Z / length;
-    }
-}
-
-// Rotate Estimated vector(s) with small angle approximation, according to the gyro data
-void rotateV(struct fp_vector *v, fp_angles_t *delta)
-{
-    struct fp_vector v_tmp = *v;
-
-    // This does a  "proper" matrix rotation using gyro deltas without small-angle approximation
-    float mat[3][3];
-    float cosx, sinx, cosy, siny, cosz, sinz;
-    float coszcosx, sinzcosx, coszsinx, sinzsinx;
-
-    cosx = cosf(delta->angles.roll);
-    sinx = sinf(delta->angles.roll);
-    cosy = cosf(delta->angles.pitch);
-    siny = sinf(delta->angles.pitch);
-    cosz = cosf(delta->angles.yaw);
-    sinz = sinf(delta->angles.yaw);
-
-    coszcosx = cosz * cosx;
-    sinzcosx = sinz * cosx;
-    coszsinx = sinx * cosz;
-    sinzsinx = sinx * sinz;
-
-    mat[0][0] = cosz * cosy;
-    mat[0][1] = -cosy * sinz;
-    mat[0][2] = siny;
-    mat[1][0] = sinzcosx + (coszsinx * siny);
-    mat[1][1] = coszcosx - (sinzsinx * siny);
-    mat[1][2] = -sinx * cosy;
-    mat[2][0] = (sinzsinx) - (coszcosx * siny);
-    mat[2][1] = (coszsinx) + (sinzcosx * siny);
-    mat[2][2] = cosy * cosx;
-
-    v->X = v_tmp.X * mat[0][0] + v_tmp.Y * mat[1][0] + v_tmp.Z * mat[2][0];
-    v->Y = v_tmp.X * mat[0][1] + v_tmp.Y * mat[1][1] + v_tmp.Z * mat[2][1];
-    v->Z = v_tmp.X * mat[0][2] + v_tmp.Y * mat[1][2] + v_tmp.Z * mat[2][2];
-}
-
 void accSum_reset(void)
 {
     accSum[0] = 0;
@@ -248,7 +198,13 @@ void acc_calc(uint32_t deltaT)
     accSumCount++;
 }
 
-// baseflight calculation by Luggi09 originates from arducopter
+/*
+* Baseflight calculation by Luggi09 originates from arducopter
+* ============================================================
+*
+* Calculate the heading of the craft (in degrees clockwise from North)
+* when given a 3-vector representing the direction of North.
+*/
 static int16_t calculateHeading(t_fp_vector *vec)
 {
     int16_t head;
@@ -259,8 +215,12 @@ static int16_t calculateHeading(t_fp_vector *vec)
     float sinePitch = sinf(anglerad[AI_PITCH]);
     float Xh = vec->A[X] * cosinePitch + vec->A[Y] * sineRoll * sinePitch + vec->A[Z] * sinePitch * cosineRoll;
     float Yh = vec->A[Y] * cosineRoll - vec->A[Z] * sineRoll;
-    float hd = (atan2f(Yh, Xh) * 1800.0f / M_PI + magneticDeclination) / 10.0f;
+    //TODO: Replace this comment with an explanation of why Yh and Xh can never simultanoeusly be zero,
+    // or handle the case in which they are and (atan2f(0, 0) is undefined.
+    float hd = (atan2f(Yh, Xh) * 1800.0f / M_PIf + magneticDeclination) / 10.0f;
     head = lrintf(hd);
+
+    // Arctan returns a value in the range -180 to 180 degrees. We 'normalize' negative angles to be positive.
     if (head < 0)
         head += 360;
 
@@ -318,8 +278,8 @@ static void getEstimatedAttitude(void)
     // Attitude of the estimated vector
     anglerad[AI_ROLL] = atan2f(EstG.V.Y, EstG.V.Z);
     anglerad[AI_PITCH] = atan2f(-EstG.V.X, sqrtf(EstG.V.Y * EstG.V.Y + EstG.V.Z * EstG.V.Z));
-    inclination.values.rollDeciDegrees = lrintf(anglerad[AI_ROLL] * (1800.0f / M_PI));
-    inclination.values.pitchDeciDegrees = lrintf(anglerad[AI_PITCH] * (1800.0f / M_PI));
+    inclination.values.rollDeciDegrees = lrintf(anglerad[AI_ROLL] * (1800.0f / M_PIf));
+    inclination.values.pitchDeciDegrees = lrintf(anglerad[AI_PITCH] * (1800.0f / M_PIf));
 
     if (sensors(SENSOR_MAG)) {
         rotateV(&EstM.V, &deltaGyroAngle);
@@ -338,16 +298,21 @@ static void getEstimatedAttitude(void)
     acc_calc(deltaT); // rotate acc vector into earth frame
 }
 
-// correction of throttle in lateral wind,
+// Correction of throttle in lateral wind.
 int16_t calculateThrottleAngleCorrection(uint8_t throttle_correction_value)
 {
     float cosZ = EstG.V.Z / sqrtf(EstG.V.X * EstG.V.X + EstG.V.Y * EstG.V.Y + EstG.V.Z * EstG.V.Z);
 
-    if (cosZ <= 0.015f) { // we are inverted, vertical or with a small angle < 0.86 deg
+    /*
+    * Use 0 as the throttle angle correction if we are inverted, vertical or with a
+    * small angle < 0.86 deg
+    * TODO: Define this small angle in config.
+    */
+    if (cosZ <= 0.015f) {
         return 0;
     }
     int angle = lrintf(acosf(cosZ) * throttleAngleScale);
     if (angle > 900)
         angle = 900;
-    return lrintf(throttle_correction_value * sinf(angle / (900.0f * M_PI / 2.0f)));
+    return lrintf(throttle_correction_value * sinf(angle / (900.0f * M_PIf / 2.0f)));
 }
diff --git a/src/main/flight/imu.h b/src/main/flight/imu.h
index de5ac89f01..552093508d 100644
--- a/src/main/flight/imu.h
+++ b/src/main/flight/imu.h
@@ -30,7 +30,7 @@ typedef struct imuRuntimeConfig_s {
     int8_t small_angle;
 } imuRuntimeConfig_t;
 
-void configureImu(imuRuntimeConfig_t *initialImuRuntimeConfig, pidProfile_t *initialPidProfile, accDeadband_t *initialAccDeadband);
+void configureIMU(imuRuntimeConfig_t *initialImuRuntimeConfig, pidProfile_t *initialPidProfile, accDeadband_t *initialAccDeadband);
 
 void calculateEstimatedAltitude(uint32_t currentTime);
 void computeIMU(rollAndPitchTrims_t *accelerometerTrims, uint8_t mixerMode);
diff --git a/src/main/flight/navigation.c b/src/main/flight/navigation.c
index 9eb5627e79..dd09430562 100644
--- a/src/main/flight/navigation.c
+++ b/src/main/flight/navigation.c
@@ -163,7 +163,7 @@ static int32_t get_D(int32_t input, float *dt, PID *pid, PID_PARAM *pid_param)
 
     // Low pass filter cut frequency for derivative calculation
     // Set to  "1 / ( 2 * PI * gps_lpf )
-    float pidFilter = (1.0f / (2.0f * M_PI * (float)gpsProfile->gps_lpf));
+    float pidFilter = (1.0f / (2.0f * M_PIf * (float)gpsProfile->gps_lpf));
     // discrete low pass filter, cuts out the
     // high frequency noise that can drive the controller crazy
     pid->derivative = pid->last_derivative + (*dt / (pidFilter + *dt)) * (pid->derivative - pid->last_derivative);
diff --git a/src/main/main.c b/src/main/main.c
index d2584fdba4..a30a6bfe94 100644
--- a/src/main/main.c
+++ b/src/main/main.c
@@ -104,7 +104,7 @@ void beepcodeInit(failsafe_t *initialFailsafe);
 void gpsInit(serialConfig_t *serialConfig, gpsConfig_t *initialGpsConfig);
 void navigationInit(gpsProfile_t *initialGpsProfile, pidProfile_t *pidProfile);
 bool sensorsAutodetect(sensorAlignmentConfig_t *sensorAlignmentConfig, uint16_t gyroLpf, uint8_t accHardwareToUse, int8_t magHardwareToUse, int16_t magDeclinationFromConfig);
-void imuInit(void);
+void initIMU(void);
 void displayInit(rxConfig_t *intialRxConfig);
 void ledStripInit(ledConfig_t *ledConfigsToUse, hsvColor_t *colorsToUse, failsafe_t* failsafeToUse);
 void loop(void);
@@ -264,7 +264,7 @@ void init(void)
     LED0_OFF;
     LED1_OFF;
 
-    imuInit();
+    initIMU();
     mixerInit(masterConfig.mixerMode, masterConfig.customMixer);
 
 #ifdef MAG
diff --git a/src/test/Makefile b/src/test/Makefile
index 8e376ea51b..5001c57230 100644
--- a/src/test/Makefile
+++ b/src/test/Makefile
@@ -149,6 +149,7 @@ flight_imu_unittest : \
 	$(OBJECT_DIR)/flight/imu.o \
 	$(OBJECT_DIR)/flight/altitudehold.o \
 	$(OBJECT_DIR)/flight_imu_unittest.o \
+	$(OBJECT_DIR)/common/maths.o \
 	$(OBJECT_DIR)/gtest_main.a
 
 	$(CXX) $(CXX_FLAGS) -lpthread $^ -o $(OBJECT_DIR)/$@
diff --git a/src/test/unit/flight_imu_unittest.cc b/src/test/unit/flight_imu_unittest.cc
index 67425aa63d..44aada0687 100644
--- a/src/test/unit/flight_imu_unittest.cc
+++ b/src/test/unit/flight_imu_unittest.cc
@@ -85,18 +85,8 @@ void updateAccelerationReadings(rollAndPitchTrims_t *rollAndPitchTrims)
     UNUSED(rollAndPitchTrims);
 }
 
-int32_t applyDeadband(int32_t, int32_t) { return 0; }
-
 uint32_t micros(void) { return 0; }
 bool isBaroCalibrationComplete(void) { return true; }
 void performBaroCalibrationCycle(void) {}
 int32_t baroCalculateAltitude(void) { return 0; }
-int constrain(int amt, int low, int high)
-{
-    UNUSED(amt);
-    UNUSED(low);
-    UNUSED(high);
-    return 0;
-}
-
 }