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jdibenes / hl2ss

HoloLens 2 Sensor Streaming. Real-time streaming of HoloLens 2 sensor data over WiFi. Research Mode and External USB-C A/V supported.
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Question about the IMU calibration matrices #117

Open zijianh4 opened 1 month ago

zijianh4 commented 1 month ago

Hi, Thanks for the awesome work! I am currently trying to calibrate the IMU sensors with cameras. However, I find that the extrinsic parameters of the accelerator is 

[[-0.9814974  -0.15415965  0.1135679   0.        ]
 [ 0.07882602  0.21521354  0.9733805   0.        ]
 [-0.17449735  0.9643225  -0.19907974  0.        ]
 [ 0.01642743  0.04962904  0.11200297  1.        ]]

and the extrinsic parameters of the gyroscope is 

[[ 0.9795797   0.16419245  0.11603672  0.        ]
 [-0.07659374 -0.22886042  0.9704413   0.        ]
 [ 0.18589534 -0.95951223 -0.2116109   0.        ]
 [ 0.          0.          0.          1.        ]]

and thus I have two questions about this 1) why are these two sensors have different extrinsic matrices? 2) why there is no data in the translation part of the gyroscope's extrinsic matrix? Thanks!

jdibenes commented 1 month ago

Hello, I don't know, sorry. I tried looking in the HoloLens2ForCV repo but was unable to find any relevant information. I assume 1) is due to them being two separate physical devices and 2) since it is used to measure orientation changes, translation is not used to transform rotation matrices, but this is just speculation.

zijianh4 commented 1 week ago

Hello, I don't know, sorry. I tried looking in the HoloLens2ForCV repo but was unable to find any relevant information. I assume 1) is due to them being two separate physical devices and 2) since it is used to measure orientation changes, translation is not used to transform rotation matrices, but this is just speculation.

Thanks for your reply. I personally also hold this idea. However, if this is the case, then it seems that we can not use this IMU data with cameras especially the gyroscope part. This is because the translation part is important when we use the gyroscope readings to do pose estimation such as SLAM algorithm.