Conventions¶

Terminology¶

1. A pose is the position of a given frame with respect to a reference frame. Whenever one writes or says the word "pose", one must say the "pose of which frame with respect to which frame".
2. A transform is the 3D transformation from one frame to an other one. Whenever one writes or says the word "transform", one must say the "transform from which frame to which frame".

Note these two words are exactly the same concept, they denote the same data structure. They can be used indifferently, provided one use them according to the convention above.

Definition of the various frames¶

Note: of course all Cartesian frames are right-handed (direct).

Terrain related frames¶

• The World Frame (aka the absolute frame) is a frame attached to the considered terrain, which never moves. The convention is the East-North-Up (ENU): the x axis points eastwards, the y axis points northward, and the z axis points up. Its origin is located at the surface that models the considered planet shape (WGS84 currently on Earth, which is close to the mean sea level).
• The Site Frame is a fixed frame associated to an area in which the rover evolves. It follows the ENU convention, with an altitude reference local to the site (note that often the site frame and world frame are considered to be the same)
• The Mission Frame is a frame defined locally

Robot related frames¶

• The Robot Body Frame (aka the RBF) is a frame attached to the robot body. Its origin is the center of the robot, at the ground level when the robot lies on a flat ground. Its x axis points forward, its y axis points leftward, and z axis points upward

• Sensor Frame
  • Camera
  • Stereovision
  • Lidar