- public void rotate(double dt, double x, double y, double z) {
- AltosQuaternion rot = AltosQuaternion.half_euler(x * dt / 2.0, y * dt / 2.0, z * dt / 2.0);
+ /* Compute azimuth angle from a reference line pointing out the side
+ * of the airframe
+ *
+ * rot = ao_rotation * x_axis * ao_rotation°
+ * rot = ao_rotation * (0,1,0,0) * ao_rotation°
+ * = (-a.x, a.r, a.z, -a.y) * (a.r, -a.x, -a.y, -a.z) . x
+ * = (-a.x * -a.x) + (a.r * a.r) + (a.z * -a.z) - (-a.y * -a.y)
+ * = a.x² + a.r² - a.z² - a.y²
+ *
+ * = (-a.x, a.r, a.z, -a.y) * (a.r, -a.x, -a.y, -a.z) . y
+ * = (-a.x * -a.y) - (a.r * -a.z) + (a.z * a.r) + (-a.y * -a.x)
+ * = a.x * a.y + a.r * a.z + a.z * a.r + a.y * a.x
+ *
+ * The X value will be the cosine of the rotation. The Y value will be the
+ * sine of the rotation; use the sign of that to figure out which direction from
+ * zero we've headed
+ */
+
+ public double azimuth() {
+ double rotx = rotation.x * rotation.x + rotation.r * rotation.r - rotation.z * rotation.z - rotation.y * rotation.y;
+ double roty = rotation.x * rotation.y + rotation.r * rotation.z + rotation.z * rotation.r + rotation.y * rotation.x;
+
+ double az = Math.acos(rotx) * 180.0 / Math.PI;
+ if (roty < 0)
+ return -az;
+ return az;
+ }
+
+ /* Given euler rotations in three axes, perform a combined rotation using
+ * quaternions
+ */
+ public void rotate(double x, double y, double z) {
+ AltosQuaternion rot = AltosQuaternion.euler(x, y, z);