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baidu / boteye

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interesting drift in Z direction #47

Open johnjin404 opened 5 years ago

johnjin404 commented 5 years ago

Sorry to bother u,,, I got an interesting scene when i test the app_tracking program by pushing a small cart in a flat hallway of my school building..., i get the pose(px,py,pz&qw,qx,qy,qz) result by UDP transportation , and change it to ros-path type, and show it in RViz...The result is interesting that the position-z changes a lot(growing) with going forward ..Previous test in a playground also has the scene, but i think it is the reason that playground is not flat ,imu performance would get worse with the body shake..More interesting is that pz grows with going forward, and decrease with going backward(ahhh...seems like correct, seems like the origin is where zero point,,,Maybe it is because the different gravity parameter between Beijing and Shanghai )...I got some pics showing below..How to avoid this problem?,,,Thank u for your explaination!! 1 2 3 4 5

mingyux commented 5 years ago

Thanks for you feedback. The z-drift is due to the incorrect IMU-camera calibration. However, it can be tricky to perform the IMU extrinsic calibration, so we simply assume it's identity as the factory calibration. Please try Kalibr (need extra steps) to do the extrinsic calibraiton.

johnjin404 commented 5 years ago

ok.thank u...observing from the calib file, seems like I need to change the extrinsic param "D_T_C_r"..I would retry to calibrate it by kalibr

mingyux commented 5 years ago

D_T_C_l: CamLeft to Device D_T_C_r: CamRight to Device D_T_I: Imu to Device In our typical setup, we set the CamLeft as Device. {Cl} and {I} should be aligned on the sensor (close to Identity).

johnjin404 commented 5 years ago

report-imucam-homelingdata.pdf here is my kalibr calibration result,,,the reprojection error is around 0.5pix ,,and seems like the timeshift between cam and imu is very bad(i don't know why..) Anyway, i change the D_T_I(IMU frame to Device or CamL) from identity to

mingyux commented 5 years ago

The kalibr result looks reasonable. It will be helpful to record some data and share w/ us. You may email us at ext_roboticvision@baidu.com.