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I have a raspberry Pi 2 with ubuntu mate and ROS Kinetic. I have a hokuyo lidar connected to it. I launch hokuyo driver, then launch hector slam and I get the map on rviz. Pi is a wifi AP with the IP 10.42.0.1.

Then I connect my laptop to PI AP and get IP 10.42.0.73 I config my hosts with the hostname and IP (laptop hostname and IP on pi's hosts file and pi hostname and IP on laptop's hosts file). Then I run

export ROS_MASTER_URI=http://10.42.0.1:11311
export ROS_IP=10.42.0.73

and launch hector slam in my laptop. I get several

[ INFO] [1518225170.720882952]: lookupTransform base_link to laser timed out. Could not transform laser scan into base_frame.

and one

[ WARN] [1518225097.231782411]: No transform between frames /map and scanmatcher_frame available after 20.003299 seconds of waiting. This warning only prints once.

In rviz I get Global Status Error

Fixed Frame [map] does not exist

I run

rosrun rqt_tf_tree rqt_tf_tree

and see that there is a base_link -> laser tf, but there is not a map -> base_link tf and there is not map ->scanmatcher_frame tf (if I run rqt_tf_tree on Raspberry PI I can see those 3 tf). So running hector slam from another PC seems to not work ok.

But, thas is not all. If I reconfigure my network and use an external router (my home router, connected to internet) letting my PI and my laptop connected to the router, then reconfigure hosts, and master_uri, I get hector slam working on my laptop.

But, yesterday I take my router, go to the place where I need to map (out of my hosue) and again, it did not work.

So it is killing my head. I need that rasp Pi could run lidar node, then connect with my laptop and run hector slam to see the map.

Thank

EDIT:

I test netcat in both directions and I can get send a receive msg.

I can run

rostopic echo /scan

and see laser scan msg

but I get

[ INFO] [1518295555.916898046]: lookupTransform base_link to laser timed out. Could not transform laser scan into base_frame.

on my laptop.

I run roswtf and get

Loaded plugin tf.tfwtf
No package or stack in context
================================================================================
Static checks summary:

Found 1 error(s).

ERROR Not all paths in ROS_PACKAGE_PATH [/home/elgarbe/catkin_ws/src/camera_umd/camera_umd:/home/elgarbe/catkin_ws/src/gscam:/home/elgarbe/catkin_ws/src/hector_slam/hector_imu_attitude_to_tf:/home/elgarbe/catkin_ws/src/hector_slam/hector_imu_tools:/home/elgarbe/catkin_ws/src/hector_slam/hector_map_tools:/home/elgarbe/catkin_ws/src/hector_slam/hector_compressed_map_transport:/home/elgarbe/catkin_ws/src/hector_slam/hector_mapping:/home/elgarbe/catkin_ws/src/hector_slam/hector_marker_drawing:/home/elgarbe/catkin_ws/src/hector_slam/hector_nav_msgs:/home/elgarbe/catkin_ws/src/hector_slam/hector_geotiff:/home/elgarbe/catkin_ws/src/hector_slam/hector_geotiff_plugins:/home/elgarbe/catkin_ws/src/hector_slam/hector_map_server:/home/elgarbe/catkin_ws/src/hector_slam/hector_slam:/home/elgarbe/catkin_ws/src/hector_slam/hector_slam_launch:/home/elgarbe/catkin_ws/src/hector_slam/hector_trajectory_server:/home/elgarbe/catkin_ws/src/camera_umd/jpeg_streamer:/home/elgarbe/catkin_ws/src/laser_proc:/home/elgarbe/catkin_ws/src/ros_best_practices/ros_package_template:/home/elgarbe/catkin_ws/src/test_leo:/home/elgarbe/catkin_ws/src/urg_c:/home/elgarbe/catkin_ws/src/urg_node:/home/elgarbe/catkin_ws/src/usb_cam:/home/elgarbe/catkin_ws/src/camera_umd/uvc_camera:/opt/ros/kinetic/share] point to an existing directory: 
 * /home/elgarbe/catkin_ws/src/gscam

================================================================================
Beginning tests of your ROS graph. These may take awhile...
analyzing graph...
... done analyzing graph
running graph rules...
... done running graph rules
running tf checks, this will take a second...
... tf checks complete

Online checks summary:

Found 1 warning(s).
Warnings are things that may be just fine, but are sometimes at fault

WARNING The following node subscriptions are unconnected:
 * /hector_mapping:
   * /syscommand
   * /tf_static
 * /hector_trajectory_server:
   * /tf_static
 * /hector_geotiff_node:
   * /syscommand
 * /rviz:
   * /trajectory
   * /tf_static
   * /map_updates

so, there are some unconected subscriptions, but don't know why!!!!

My hector_mapping launch file is

<launch>
  <arg name="tf_map_scanmatch_transform_frame_name" default="scanmatcher_frame"/>
  <arg name="base_frame" default="base_link"/>
  <arg name="odom_frame" default="base_link"/>
  <arg name="pub_map_odom_transform" default="true"/>
  <arg name="scan_subscriber_queue_size" default="5"/>
  <arg name="scan_topic" default="scan"/>
  <arg name="map_size" default="2048"/>
  
  <node pkg="hector_mapping" type="hector_mapping" name="hector_mapping" output="screen">
    
    <!-- Frame names -->
    <param name="map_frame" value="map" />
    <param name="base_frame" value="$(arg base_frame)" />
    <param name="odom_frame" value="$(arg odom_frame)" />
    
    <!-- Tf use -->
    <param name="use_tf_scan_transformation" value="true"/>
    <param name="use_tf_pose_start_estimate" value="false"/>
    <param name="pub_map_odom_transform" value="$(arg pub_map_odom_transform)"/>
    
    <!-- Map size / start point -->
    <param name="map_resolution" value="0.050"/>
    <param name="map_size" value="$(arg map_size)"/>
    <param name="map_start_x" value="0.5"/>
    <param name="map_start_y" value="0.5" />
    <param name="map_multi_res_levels" value="2" />
    
    <!-- Map update parameters -->
    <param name="update_factor_free" value="0.4"/>
    <param name="update_factor_occupied" value="0.9" />    
    <param name="map_update_distance_thresh" value="0.4"/>
    <param name="map_update_angle_thresh" value="0.06" />
    <param name="laser_z_min_value" value = "-1.0" />
    <param name="laser_z_max_value" value = "1.0" />
    
    <!-- Advertising config --> 
    <param name="advertise_map_service" value="true"/>
    
    <param name="scan_subscriber_queue_size" value="$(arg scan_subscriber_queue_size)"/>
    <param name="scan_topic" value="$(arg scan_topic)"/>
    
    <!-- Debug parameters -->
    <!--
      <param name="output_timing" value="false"/>
      <param name="pub_drawings" value="true"/>
      <param name="pub_debug_output" value="true"/>
    -->
    <param name="tf_map_scanmatch_transform_frame_name" value="$(arg tf_map_scanmatch_transform_frame_name)" />
  </node>
<!--    
  <node pkg="tf" type="static_transform_publisher" name="map_baselink_broadcaster" args="0 0 0 0 0 0 map scanmatcher_frame 100"/>
    -->

  <node pkg="tf" type="static_transform_publisher" name="map_nav_broadcaster" args="0 0 0 0 0 0 base_link laser 50"/>
</launch>

you can see that I'm using base_link to laser tf, and it is showed in rqt_view_frames

So, I'm really out of ideas here...

Originally posted by elgarbe on ROS Answers with karma: 106 on 2018-02-09

Post score: 0

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Ok, problem solved, it was a date/time problem between raspberry pi and my laptop. When I use my router, both sinchronize with internet and so it work. Then, when I setup raspberri pi as AP, reboot and connect my laptop to PI, raspberry has an old date/time, and so don't work.

The answer was right there all of the time: http://wiki.ros.org/ROS/NetworkSetup chapter 5

Originally posted by elgarbe with karma: 106 on 2018-02-10

This answer was ACCEPTED on the original site

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