fixedframe

Fixedframe is a term used in robotics, computer vision, and physics to denote a reference frame anchored to the environment rather than to a moving body. It is commonly referred to as the world frame or map frame in robotics. In this frame, the coordinates of points, sensors, and objects are expressed relative to a stable external reference.

In contrast, moving frames are attached to a robot or object and move with it. Transformations between frames are described by homogeneous transformation matrices or by rotation matrices and translation vectors. The pose of a moving object in the fixed frame is obtained by composing its local pose with the fixed-frame coordinates. This relationship underpins many calculations in navigation, perception, and control.

Applications and usage. In SLAM (simultaneous localization and mapping), a fixed world frame provides a global reference for mapping and localization. Sensor data from cameras, LIDAR, or radar are transformed into the fixed frame for fusion and interpretation. In robotics software ecosystems, a fixed frame is often labeled as map or world, while other frames (such as base_link, camera, or end_effector) are defined relative to it.

Notes and considerations. The fixed frame is ideally static with respect to the environment, but in dynamic settings the frame itself may be defined relative to a moving environment or updated over time. The choice of fixed frame affects the interpretation of measurements and the design of control and estimation algorithms. When selecting a fixed frame, practitioners consider stability, simplicity of transformations, and consistency across system components.