## What this teaches
How to unable to build ORB_SLAM3 with ROS using ./build_ros.sh on ubuntu 20.04 with ros-noetic-desktop-full.
## The problem
Issue UZ-SLAMLab/ORB_SLAM3#913 (closed, 9 comments): I have installed ros-noetic-desktop-full Paths for ros_root and ros_package are echo $ROS_ROOT /opt/ros/noetic/share/ros echo $ROS_PACKAGE_PATH /opt/ros/noetic/share:~/ORB_SLAM3/Examples_old/ROS/ORB_SLAM3 after running ./build_ros.sh, I get [rosbuild] Building package ORB_SLAM3 Failed to invoke /opt/ros/noetic/bin/rospack deps-manifests ORB_SLAM3 ModuleNotFoundError: No module named 'rosdep2' [rospack] Error: could not find python module 'rosdep2.rospack'. is rosdep up-to-date (at least 0.10.4)? CMake Error at /opt/ros/noetic/share/ros/core/rosbuild/public.
## What worked (verified answer)
The ORB_SLAM3 ROS build failing with 'No module named rosdep2' (and rospack errors) was fixed by the reporter with a clean reinstall: purge ros-noetic from the system and reinstall it using the standard ROS Noetic Ubuntu install instructions. The broken install was the problem, not the ORB_SLAM3 build itself.
## Source
gh:UZ-SLAMLab/ORB_SLAM3#913 - https://github.com/UZ-SLAMLab/ORB_SLAM3/issues/913