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# rs-imu-calibration Tool:
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## Goal
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The tool is intended to calibrate the IMU built in D435i cameras
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## Description
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D435i cameras arrive from the factory with a calibrated IMU device. However the calibration accuracy can be further imporved by a calibration procedure.
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The rs-imu-calibration tool is a code example that walks you through the calibration steps and saves the calibration coefficients to the EEPROM, to be applied automatically by the driver.
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Detailed information, including installation, procedure, and sample calibration demonstration, is described in the following white paper:
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IMU Calibration Tool for Intel® RealSense™ Depth Camera White Paper
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https://dev.intelrealsense.com/docs/imu-calibration-tool-for-intel-realsense-depth-camera
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## Limitations
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While the tool achieves good overall results, it has limitations that may impact accuracy. Please refer to the above white paper for further information.
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## Command Line Parameters
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|Flag |Description |Default|
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|-----|---|---|
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|`-h `|Show help. ||
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|`-i <accel_filename> [gyro_filename]`| Load previously saved results to EEPROM| |
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|`-s serial_no`| calibrate device with given serial_no| calibrate first found device|
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|`-g `|show graph of data before and after calibration| ||
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# Calibration Procedure:
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Running:
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`python rs-imu-calibration.py`
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The script runs you through the 6 main orientations of the camera.
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For each direction there are the following steps:
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* **Rotation:**<br>
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* The script prints the following line, describing how to orient the camera:<br>
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`Align to direction: [ 0. -1. 0.] Mounting screw pointing down, device facing out`<br>
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* Then it prints the status (rotate) and the difference from the desired orientation:<br>
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`Status.rotate: [ 1.0157 -0.1037 0.9945]: [False False False]`<br>
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* You have to bring the numbers to [0,0,0] and then you are in the right direction and the script moves on to the next status.<br><br>
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* **Wait to Stablize:**<br>
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* The script waits for you to be stable for 3 seconds. Meanwhile there is a countdown message:<br>
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`Status.wait_to_stable: 2.8 (secs)`<br>
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* When waited for 3 seconds, the script begin to <b>collect data:<br><br>
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* **Collecting data:**<br>
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* Status line is a line of dots. When reaching 20 dots, enough data is collected and script carries on to next orientation.<br>
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* If camera is no longer in the precise orientation, data is not collected.
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* If camera is moved too much, going back to <b>Rotation status.
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When done all 6 orientations, the following message appears, suggesting you to save the raw data gathered:<br>
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`Would you like to save the raw data? Enter footer for saving files (accel_<footer>.txt and gyro_<footer>.txt)`<br>
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`Enter nothing to not save raw data to disk. >`<br>
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Either press “Enter” not to save or an ending (like 2 or <serial_no>_1) to save the accel.txt, gyro.txt.<br>
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The files can be loaded using the “-i” option.
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Then the script will ask to save the data to the Device.<br>
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Choose Y (or any other combination with Y or y in it) to save.
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That’s it. At the end a confirmation message appears:<br>
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`SUCCESS: saved calibration to camera.`
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**NOTICE:**<br>
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Press ESC key to abort the calibration process.
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CTRL-C isn’t working so press CTRL-Z and then `kill -9 %1` if you want to terminate in the middle…
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**Appendix A:**<br>
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I found it a little challenging to hold the camera in the precise 90 degrees angle needed.
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Therefor I used my original camera's box as a camera holder.
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I cut a little piece so the cord may come out, and that's it:<br>
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***open box image:***<br>
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<br>
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***camera in box:***<br>
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<br>
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***face down position:***<br>
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<br>
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***cord up position:***<br>
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<br>
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***upright facing out (or upside down facing out, depends on which side the cord is..):***<br>
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<br>
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***cord down position:***<br>
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<br>
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***upside down (or upright) facing out:***<br>
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