Skip to main content
U.S. flag

An official website of the United States government

Official websites use .gov
A .gov website belongs to an official government organization in the United States.

Secure .gov websites use HTTPS
A lock ( ) or https:// means you’ve safely connected to the .gov website. Share sensitive information only on official, secure websites.

Describing a Robot



Tsai H. Hong, Michael O. Shneier


This correspondence describes a method of building and maintaining a spatial representation for the workspace of a robot, using a sensor that moves about in the world. From the know camera position at which an image is obtained, and two-dimensional silhouettes of the image, a series of cones is projected to describe the possible positions of the objects in the space. When an object is seen from several viewpoints, the intersections of the cones constrain the position and size of the object. After several views have been processed, the representation of the object begins to resemble its true shape. At all times, the spatial representation containss the best guess at the true situation in the world with uncertainties in position and shape explicitly represented. An octree is used as the data structure for the representation. It not only provides a relatively compact representation, but also allows fast access to information and enables large parts of the workspace to be ignored. The purpose of constructing this representation is not so much to recognize objects as to describe the volumes in the workspace that are occupied and those that are empty. This enables trajectory planning to be carried out, and also provides a means of spatially indexing objects without needing to represent the objects at an extremely fine resolution. The spatial representation is one part of a complex representation of the workspace used by the sensory system of a robot manipulator in understanding its environment.
IEEE Transactions on Pattern Analysis and Machine Intelligence
PAMI-7 No.6


3-D Reconstruction, Octrees


Hong, T. and Shneier, M. (1985), Describing a Robot, IEEE Transactions on Pattern Analysis and Machine Intelligence, [online], (Accessed June 20, 2024)


If you have any questions about this publication or are having problems accessing it, please contact

Created November 28, 1985, Updated October 12, 2021