In carter_sim, why is pose a size 7 array?

Taking a look under:, we see:
“actors”: [
“name”: “test_carter”,
“reference”: “URDF’carter/urdf/carter.urdf’”,
“pose”: [1, 0, 0, 0, 0, 0, 0]

Why is pose a size 7 array?

Pose vector means [rotation_quaternion_w, rotation_quaternion_x, rotation_quaternion_y, rotation_quaternion_z, translation_x, translation_y, translation_z] with respect to the world coordinate system and note that [translation_x, translation_y, translation_z] is in meter not centimetre.