Robotics
Occupancy grid
Definition
An occupancy grid divides space into cells and records occupancy information for each cell. A two-dimensional robot map commonly distinguishes occupied, free, and unknown regions.
Also known as: Occupancy grid map
Updated
A map made of cells
An occupancy grid offers a discrete representation that navigation software can inspect. The ROS OccupancyGrid specification defines a two-dimensional array with application-dependent cell values, including a conventional unknown value. Numeric encodings should therefore be checked for the producing application.
A robot can use such a map to represent walls, open floor, and areas that have not been observed. Unknown space is different from measured free space.
Resolution sets the scale
MapMetaData records resolution in metres per cell, grid dimensions, and the map origin. Fine cells represent smaller features but require more cells to cover the same area. A cell index is not itself a physical coordinate until these metadata are applied.
Occupancy is only part of planning
A grid does not by itself describe a robot's full shape or movement constraints. For a humanoid, a two-dimensional floor map also omits much of the vertical structure relevant to arms and head clearance. Motion planning needs to interpret the map alongside robot geometry and the constraints of the intended motion.
Sources
Related terms
Simultaneous localization and mapping
Simultaneous localization and mapping is the joint estimation of a robot's state and a map of its environment from sensor observations. It is commonly abbreviated SLAM.
Motion planning
Motion planning finds a robot movement from an initial state to a goal while satisfying constraints such as collision avoidance. A planner may produce a geometric path, a timed trajectory, or a sequence of controls.
Signed distance field
A signed distance field represents a surface by assigning spatial locations a distance value whose sign distinguishes the two sides of the surface. Its zero level marks the surface, while the sign convention depends on the representation.