Data & collection
Sensor calibration
Sensor calibration is the estimation and documentation of parameters that map raw sensor readings into physically meaningful values and known spatial relationships. In robotics it can include scale, bias, distortion, intrinsic camera parameters, sensor-to-sensor or sensor-to-robot transforms, and timing offsets. Calibration does not remove all noise or drift.
Also known as: robot sensor calibration, sensor calibrations
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Calibration gives raw readings a model
A camera calibration may estimate focal length, principal point and lens distortion so image pixels can be projected geometrically. Zhang's planar calibration method estimates intrinsic and extrinsic parameters from several views of a known pattern.
Other sensors need different models. An IMU may require bias and scale estimates; a force-torque sensor needs a calibration matrix, zero offset and reference frame; a depth camera needs metric scale and intrinsics. The required parameters depend on what the downstream system must infer.
Extrinsic and hand-eye calibration connect devices
Extrinsic calibration estimates the rigid transform between coordinate frames. Hand-eye calibration determines the relationship between a camera and a robot hand, tool or base. The classic Tsai-Lenz method addresses this spatial relationship using robot and camera motions.
Spatial calibration does not solve temporal alignment. Two cameras can be geometrically calibrated yet capture different instants. A complete multimodal rig may need both extrinsic transforms and measured clock or trigger offsets.
Calibration belongs with the dataset
DROID includes camera calibration alongside synchronised views and robot data. Without the relevant files, a buyer may be unable to reconstruct 3D geometry or express observations in the robot frame.
A dataset should state the calibration target, procedure, software, units, reference frames, date or session, residual error and any recalibration after hardware moved. Raw data should retain the calibration version that applied during capture. Calibration quality can degrade through impact, temperature, wear or sensor remounting even when the file format stays unchanged.
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Related terms
Hardware & control
Coordinate frame
A coordinate frame is a defined origin and set of oriented axes used to express positions, orientations, motions, forces, or other spatial quantities. A value has no complete geometric meaning until its frame and convention are known. Transformations relate measurements expressed in frames such as world, robot base, camera, end effector, object, or sensor.
Data & collection
Depth data
Depth data records the distance associated with image locations or sensor rays, usually as a depth image in which each pixel stores a metric value relative to a camera. The exact geometry, units, invalid-value convention, and coordinate frame depend on the sensor and encoding. RGB-D data pairs depth with colour imagery; a point cloud is a separate 3D representation derived from or aligned with such measurements.
Data & collection
Data synchronisation
Data synchronisation is the process of placing sensor, state, action, annotation, and outcome records on a common timeline so samples that describe the same physical instant or transition can be matched. It requires trustworthy timestamps or trigger relationships and an explicit rule for handling streams with different rates, delays, dropped samples, and clock offsets.
Hardware & control
Tactile sensing
Tactile sensing is the detection and measurement of physical contact properties at a robot's surface or contact interface. Depending on the sensor, it can report pressure or force distribution, contact location, shear, vibration, slip, texture, temperature, or deformation. Tactile data complements vision by measuring interactions that may be hidden at the point of contact.
Hardware & control
Force–torque sensing
Force–torque sensing is the measurement of forces and rotational moments transmitted through a robot interface, commonly with a six-axis sensor reporting three force components and three torque components. The combined quantity is a wrench expressed at a specified origin and in a specified coordinate frame. It measures the resultant load at the sensor, not a spatial pressure map across every contact.