query about accelerometer data (offset correction and unit conversion)

[ihtishamaliktk]

Hi, The Accelerometer offset correction [926.447738516 -15.4401130742 -401.003545936] used in the _imuconvertion.py is different than the offset given in the calibration file which is [24.13, 4.88, -24.93]. Is there any unit conversion that I am missing?

Secondly, the raw data format says that accelerometer values are in mg (milli-g). Shouldn't then mg be first converted to g and then to m/s² in _imuconvertion.py?

Thank you

[taihup]

Hi, the valid values are those in the yaml configuration file. Please see the function modify_imu_data()inside create_bagfile.py script. There you can check how the offset is applied and how the unit conversion is done.

Note: We found some issues related to the IMU measurements (they are not uniformly distributed as it is expected (caused by how we recorded the data) and there are some moments where the IMU gives null measurements with white noise (seems to be a hardware issue in the TARA). We are working on solving these issues and we are going to update the dataset soon (we don't have an estimated date but should be in the next months).

[ihtishamaliktk]

I missed going through create_bagfile.py. Its more informative. Thank you Best of luck with the imu data fix.

[huanhexiao]

@taihup hi buddy, may i ask where are u about the dataset update?

[taihup]

Hi guys, we are still working on it, I will post here when we upload the fixed data.

[huanhexiao]

@taihup hi bro, is the dataset availible now?

[taihup]

Not yet. We will post here as soon as there is news.

[kzamzam]

@taihup are the bag files available on the website created using the create_bagfile.py. So they contain rectified images, and also the IMU values are already processed for the biases?

[taihup]

The script create_bagfile.py removes the IMU bias (check function modify_imu_data()) and rectified the images (check function rectify_images()).

[kzamzam]

@taihup I think the create_bagfile.py does not actually rectify the images, it just gets the P matrix needed for that and adds it to the camera_info topic, however, the rectification itself is not applied.

[taihup]

I think you are right, the images are not recitified but the rectify information is stores in camera_info