# Some errors when running gmapping_demo on a turtlebot

Hello!

I have a turtlebot2. And my ros distro is kinetic.

And I just tried to use it to build a map with slam, following the tutorial on the website.

Everything was OK until I entered the command roslaunch turtlebot_navigation gmapping_demo.launch

There was an error which was:

[ERROR] [1525520327.760808073]: Failed to load nodelet [/depthimage_to_laserscan] of type [depthimage_to_laserscan/DepthImageToLaserScanNodelet] even after refreshing the cache: Failed to load library /opt/ros/kinetic/lib//libDepthImageToLaserScanNodelet.so. Make sure that you are calling the PLUGINLIB_EXPORT_CLASS macro in the library code, and that names are consistent between this macro and your XML. Error string: Could not load library (Poco exception = libopencv_core3.so.3.3: cannot open shared object file: No such file or directory) [ERROR] [1525520327.760876329]: The error before refreshing the cache was: Failed to load library /opt/ros/kinetic/lib//libDepthImageToLaserScanNodelet.so. Make sure that you are calling the PLUGINLIB_EXPORT_CLASS macro in the library code, and that names are consistent between this macro and your XML. Error string: Could not load library (Poco exception = libopencv_core3.so.3.3: cannot open shared object file: No such file or directory) [FATAL] [1525520327.761157035]: Failed to load nodelet '/depthimage_to_laserscanof typedepthimage_to_laserscan/DepthImageToLaserScanNodeletto managercamera/camera_nodelet_manager' [depthimage_to_laserscan-14] process has died [pid 6103, exit code 255, cmd /opt/ros/kinetic/lib/nodelet/nodelet load depthimage_to_laserscan/DepthImageToLaserScanNodelet camera/camera_nodelet_manager image:=camera/depth/image_raw scan:=/scan camera/image:=camera/depth/image_raw camera/scan:=/scan __name:=depthimage_to_laserscan __log:=/home/ghw/.ros/log/d2db6dce-5058-11e8-99e4-2c6e85fea0ec/depthimage_to_laserscan-14.log]. log file: /home/ghw/.ros/log/d2db6dce-5058-11e8-99e4-2c6e85fea0ec/depthimage_to_laserscan-14*.log

That was weird because I've already installed the package depthimage_to_laserscan.

And when I entered rosrun depthimage_to_laserscan depthimage_to_laserscan

It said that:

/opt/ros/kinetic/lib/depthimage_to_laserscan/depthimage_to_laserscan: error while loading shared libraries: libopencv_core3.so.3.3: cannot open shared object file: No such file or directory

Did this mean that there is something wrong in the OPENCV?

And I don't know how to deal with this now.

How can I sucessfully build a map with a turtlebot2 ?

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