Attention: Answers.ros.org is deprecated as of August the 11th, 2023. Please visit robotics.stackexchange.com to ask a new question. This site will remain online in read-only mode during the transition and into the foreseeable future. Selected questions and answers have been migrated, and redirects have been put in place to direct users to the corresponding questions on Robotics Stack Exchange. Additional details are available here.

Revision history [back]

255 is the unsigned equivalent of -1. The OccupancyGrid message (http://docs.ros.org/indigo/api/nav_msgs/html/msg/OccupancyGrid.html) stores values as signed 8 bit ints - int8, while the Costmap2D object uses the char type internally (equivalent to unsigned 8 bit ints - uint8).

ROS Answers is licensed under Creative Commons Attribution 3.0 Content on this site is licensed under a Creative Commons Attribution Share Alike 3.0 license.