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-tp6986p7130.html

Hi Mathieu

Thank you for your answer

I have tried as you suggested with:

 Optimizer/Strategy=1 (g2o) and Optimizer/Strategy=2 (GTSAM) as you can see in the following figures:

This figure correspond to Optimizer/Strategy=1. I have run it many times and the rotation with respect to the grid is much better than with Optimizer/Strategy=2. However, as you can see the right wall is twisted and also the general map  has a small rotation.



This figure correspond to Optimizer/Strategy=2. I have run it many times and in general looks very good, but there are times where is rotated. The Figure shows a map where the rotation with respect to the grid is practically none.  

1. The rotation can come from the optimization with gravity constraints. I don't know if you built with both GTSAM and g2o dependencies, but GTSAM seems to make the map rotate more with gravity constraints are added (I didn't see how to avoid that). Try comparing Optimizer/Strategy=1 and Optimizer/Strategy=2.

  * Based on the previous figures, how can avoid the bending of the wall using Optimizer/Strategy=1

  * How can avoid the map rotates with respect to the grid when using Optimizer/Strategy=2

2. In databaseViewer->Constraint view, by moving the Neighbor slider, we can see odometry covariance.

  I could not find the databaseViewer->Constraint.

    I have search in Window/Show view  also in Window/Preferences

4. rtabmap provides also a visual odometry, but there are also many other packages doing VIO out there that could replace zed's odometry too and feed the resulting odometry to rtabmap.

  Which VIO package you recommend, knowing I have ZED2. And, is it possible to have an example or link

5. This is the type of feature used in the BOW vocabulary

   OK thank you, but  what exactly this parameter does ?

6. If the resulting IMU data from zed2 has a quaternion, they may already do the estimation. Otherwise, for IMUs, you can use complementary filter or madgwick  filter ros packages.

     * Do you know how to find out if ZED2 has a quaternion and may already do the estimation and how to use this estimation?

   * The madgwick package fuses imu/data_raw with imu/mag and publish imu/data. Thus, ZED2'barometer delivers /atm_press topic whic is the current atmospheric pressure in hPa (hectoPascals).

   * I was thinking to use robot_localization package. What do you think? and how shall be done  

7. In databaseViewer->Statistics panel, next to each statistic, there is a button to plot the values.

  * I see, I have found it, thank you


I am looking forward to your replay.