matlab-convert-aerospace-coordinates

Use ecef2eci and eci2ecef from Aerospace Toolbox, which transform position, velocity, and acceleration between the frames. Both require a UTC time input because ECI orientation depends on Earth's rotation at that instant.

Use angle2quat with angles in radians and an explicit rotation sequence like 'ZYX', or create a quaternion object with quaternion([yaw pitch roll], 'eulerd', 'ZYX', 'frame') for degree inputs. Aerospace Toolbox quaternions use scalar-first [w x y z] format.

angle2dcm expects radians, not degrees. Convert degree values first with deg2rad or convang(value, 'deg', 'rad'), and always specify the rotation sequence explicitly since the default is 'ZYX'.

Geodetic latitude is measured from the surface normal of the reference ellipsoid, while geocentric latitude is measured from Earth's center, differing by up to about 0.19 degrees. Convert between them with geod2geoc and geoc2geod, which expect radians.

Use quaternions for computation and interpolation because Euler angles suffer gimbal lock when the second rotation reaches plus or minus 90 degrees. Convert to Euler angles only for display, and normalize quaternions after accumulated arithmetic.

Rodrigues vectors are singular at 180-degree rotations because they encode rotation as axis times tan(theta/2). They suit small-angle optimization with three parameters, but use quaternions for arbitrary rotations, interpolation, or long integrations.