Reasoning about shadows in a mobile robot environment

Valquiria Fenelon, Paulo E. Santos, Hannah Mary Dee, Fabio G. Cozman

Research output: Contribution to journalArticlepeer-review

8 Citations (SciVal)
197 Downloads (Pure)


This paper describes a logic-based formalism for qualitative spatial reasoning with cast shadows (Perceptual Qualitative Relations on Shadows, or PQRS) and presents results of a mobile robot qualitative self-localisation experiment using this formalism. Shadow detection was accomplished by mapping the images from the robot’s monocular colour camera into a HSV colour space and then thresholding on the V dimension. We present results of self-localisation using two methods for obtaining the threshold automatically: in one method the images are segmented according to their grey-scale histograms, in the other, the threshold is set according to a prediction about the robot’s location, based upon a qualitative spatial reasoning theory about shadows. This theory-driven threshold search and the qualitative self-localisation procedure are the main contributions of the present research. To the best of our knowledge this is the first work that uses qualitative spatial representations both to perform robot self-localisation and to calibrate a robot’s interpretation of its perceptual input.
Original languageEnglish
Pages (from-to)553-565
JournalApplied Intelligence
Issue number4
Early online date21 Sept 2012
Publication statusPublished - 01 Jun 2013


  • Qualitative spatial reasoning
  • Cognitive robotics
  • Knowledge representation


Dive into the research topics of 'Reasoning about shadows in a mobile robot environment'. Together they form a unique fingerprint.

Cite this