[Question] left/right/imu parameters available?

[FaboNo]

Hi there, We would like to test the ZED2 with Kimera (https://github.com/MIT-SPARK/Kimera-VIO) and we need to provide the parameters for the IMU as well as the left and right cameras. Do you know where can I find them in the repo? Thank you

[Myzhar]

Hi @FaboNo I do not know the Kimera-VIO repository. What parameters does it need? You can get the camera parameters for the current resolution in the camera_info topic or reading the conf file in the /usr/local/zed/settings/ folder.

[FaboNo]

@Myzhar sorry, I should give you some examples, I guess the format is the one provided by Kalibr, here are two examples of yaml files:

%YAML:1.0
# General sensor definitions.
camera_id: left_cam

# Sensor extrinsics wrt. the body-frame.
T_BS:
  cols: 4
  rows: 4
  data: [0.9999696204143095, 0.0026862211395019798, 0.007317271653524808, -0.035444853724645585,
         -0.0023778583642409027, 0.9991219422040934, -0.04182930068647981, 0.027123624325323524,
         -0.007423209417859271, 0.041810630494050476, 0.9990979767468398, -0.08347299538526054,
         0.0, 0.0, 0.0, 1.0]

# Camera specific definitions.
rate_hz: 30
resolution: [640, 480]
camera_model: pinhole
intrinsics: [385.18681587014777, 385.08894038512136, 323.08215719710927, 241.75845145344397] #fu, fv, cu, cv
distortion_model: equidistant
distortion_coefficients: [0.34058661190133155, 0.10891845722051097, 0.1099073078802829, -0.029097445495854555]

And for the IMU:

%YAML:1.0
# Type of IMU preintegration:
# 0: CombinedImuFactor
# 1: ImuFactor
imu_preintegration_type: 1

# Collected by Andrew Violette on 02/19/20
# Sensor extrinsics wrt. the body-frame.
T_BS:
  cols: 4
  rows: 4
  data: [1.0, 0.0, 0.0, 0.0,
         0.0, 1.0, 0.0, 0.0,
         0.0, 0.0, 1.0, 0.0,
         0.0, 0.0, 0.0, 1.0]
rate_hz: 300

# inertial sensor noise model parameters (static)
gyroscope_noise_density: 0.000488     # [ rad / s / sqrt(Hz) ]   ( gyro "white noise" )
gyroscope_random_walk: 4.88e-05       # [ rad / s^2 / sqrt(Hz) ] ( gyro bias diffusion )
accelerometer_noise_density: 0.00147  # [ m / s^2 / sqrt(Hz) ]   ( accel "white noise" )
accelerometer_random_walk: 0.00147    # [ m / s^3 / sqrt(Hz) ].  ( accel bias diffusion )

# Extra parameters
imu_integration_sigma: 1.0e-8
imu_time_shift: 0.0
n_gravity: [0.0, 0.0, -9.81]

Do you have such format available or do I have to run kalibr to get them? I will have a look at /usr/local/zed/settings

Thanks

[Myzhar]

The # inertial sensor noise model parameters are available in the SensorParameters data structure. They are not exposed in the ROS node, but you can get them simply modifying the Sensor Data tutorial

The # Sensor extrinsics wrt. the body-frame. is available in TF, but you can get the values reading the console log when the node starts. For example:

[ INFO] [1595584347.430331450]: Camera-IMU Transform: 
 5596CB1354C0
0.999626 0.025546 0.009792 -0.002000
-0.025588 0.999664 0.004221 -0.023000
-0.009681 -0.004470 0.999943 -0.002000
0.000000 0.000000 0.000000 1.00000

The only missing information is a precise imu_time_shift, you need to run Kalibr for that.

[FaboNo]

Ok got it! thank you very much