Re: ZED2 rtabmap loop closure and twisted map

Posted by acp on
URL: http://official-rtab-map-forum.206.s1.nabble.com/ZED2-rtabmap-loop-closure-and-twisted-map-tp6986p7099.html

Dear Mathieu
As you have suggested. I have set Kp/ByteToFloat to false to get better loop closure hypotheses with binary descriptors and also Rtabmap/LoopThr to 0.06 to test more hypotheses.

Since ZED2 has an imu included /zed/zed_node/imu/data, I have feed the imu data to rtabmap.

As you can see in the following .launch


<group ns="/zed/">
    <include file="$(find rtabmap_ros)/launch/rtabmap.launch">
     <arg name="rtabmap_args"  value="--delete_db_on_start --Optimizer/GravitySigma 0.3 --Grid/3D true --Grid/RangeMax 7  --Grid/CellSize 0.3 --Grid/GroundIsObstacle true localization:=false  --Rtabmap/LoopThr 0.06  --Kp/ByteToFloat false" />



      <arg name = "rgb_topic"                value = "/zed/zed_node/rgb/image_rect_color" />
      <arg name = "depth_topic"              value = "/zed/zed_node/depth/depth_registered" />
      <arg name = "camera_info_topic"        value = "/zed/zed_node/rgb/camera_info" /> 
      <arg name = "depth_camera_info_topic"  value = "/zed/zed_node/depth/camera_info" />
      <arg name = "frame_id"                      value = "$(arg frame)" />
      <arg name = "odom_frame_id"                 value = "odom" />
      <arg name = "approx_sync"                   value = "false" />
      <arg name = "visual_odometry"               value = "false" />
      <arg name = "rtabmapviz"                    value = "false" />
      <arg name = "rviz"                          value = "false" />
      <arg name = "odom_topic"                    value = "/zed/zed_node/odom" />
      <arg name = "imu_topic"                     value = "/zed/zed_node/imu/data"/> 
      <arg name = "odom_tf_angular_variance"      value = "0.001"/>
      <arg name = "odom_tf_linear_variance"       value = "0.001"/>
     
    </include>
</group>

Also as you can see in the following figure, the gap before  the  loop closure is smaller. But still there is a big gap
 



After loop closure the map get much better and also is aligned with the floor but it  is rotated with respect to the grid.

Based on the previous I do have the following questions

1.- How can avoid the rotation of the map with the grid?

2.-Where do you see the odometry covariance  set to Identity?

3.- Why the  odometry covariance  set to Identity  is quite bad if I want good map optimizations and to reject bad loop closures?

4.-I am using ZED2's odometry as you have mentioned. However what do you suggest to get better odometry?

5 What does the Kp/DetectorStrategy does?
 
6.- Since ZED2 has barometer, magnetometer, and imu, how good would be to fuse them with kalman filters to get better estimation?

7.-How do you get the plots of the parameters?


Thank you very Much