General Information

STARMAC development generally uses aerospace frame conventions, which favors a "forward-starboard-down" body-fixed frame, whose position and orientation are expressed in terms of a "north-east-down" (NED) reference frame. Orientation is often expressed in terms of Euler angles with a rotating frame, with the usual preferred sequence being yaw-pitch-roll (z-y-x) (i.e. when using transformations.py this is the sequence 'rzyx').

TF Tree

The following diagram shows the typical tf transform tree:

Typical tf tree

V denotes the vehicle name, e.g. pelican1.

Frames

Name	Description
/enu	"East-North-Up" oriented frame at origin (typically, the Vicon origin)
/ned	"North-East-Down" oriented frame at origin
/V/flyer_vicon	Body-fixed frame on flyer corresponding to the Vicon subject's frame. Varies depending on how subject was defined in Vicon software, but typically located at a Vicon marker located aft along the longitudinal flyer axis, with X-axis pointing down, Y-axis pointing starboard, Z-axis pointing aft
/V/flyer_imu	Body-fixed frame on flyer, located along vertical centerline at location of IMU. X forward, Y starboard, Z down. If vehicle is on ground, pointed "north" then this frame is parallel to /ned
/V/flyer_frame	Body-fixed frame on flyer, origin coincident with flyer_imu but yawed by +90 deg from it. Might be useful for locating sensors on the 'square part' of a STARMAC frame.

Transforms

Parent	Child	Authority	Comments
/enu	/ned	static
/enu	/V/flyer_vicon		Vicon provides this transform
/V/flyer_vicon	/V/flyer_imu	static
/V/flyer_imu	/V/flyer_frame	static	typ. yaw of 90 deg

The following diagram shows the typical transform between /V/flyer_vicon and /V/flyer_imu:

Typical transform from flyer_vicon to flyer_imu