Implementation of an automatic method to estimate the 2D extrinsic calibration parameters of multiple sensors through their observed egomotion, explicitly handling scale ambiguity from cameras.
Authors: David Zuñiga-Noël, Jose-Raul Ruiz-Sarmiento, Ruben Gomez-Ojeda, and Javier Gonzalez-Jimenez
License: GPLv3
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Boost (1.58.0.1ubuntu1)
sudo apt install libboost-all-dev -
Ceres (1.14.0-facb199)
See ceres documentation.
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CMake (3.5.1-1ubuntu1)
sudo apt install cmake -
Eigen (3.3~beta1-2)
sudo apt install libeigen3-dev -
Gflags (2.1.2-3)
sudo apt install libgflags-dev -
Glog (0.3.4-0.1)
sudo apt install libgoogle-glog-dev
The input are synchronized per-sensor incremental 2D motions. For each sensor, incremental motions are grouped into a single text file, where each line contains a synchronized 2D incremental motion (angles in radians) in the following format:
x y yaw
Note: all sensors must have the same number of observations
To compute synchronized incremental motions from estimated trajectories, please see tools/sync.
The multisensor calibration method can be invoked as:
calibrate [options] <motions1> <motions2> ...
Notes:
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The method calibrates all sensors with respect to a reference one. The reference sensor is assumed to be the one observing the first incremetal motions.
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Use the
--scale_ambiguous=n,m,...option to indicate which motions have scale ambiguity.
To ilustrate the usage of the calibration method, we provided example trajectories in the data directory. First, the synchronous incremental motions are required. To compute then form the estimated trajectories, we strongly recomend to use the provided sync tool:
sync -s 3 --output_dir=./data data/camera.txt data/laser.txt data/wheel.txt
This command will produce three files inside the data directory: 1.txt, 2.txt, 3.txt for the camera, laser and wheel odometry, respectively. These files contain the synchronized incremental motions for each sensor.
To perform the extrinsic calibration with respect to the wheel odometry, run
calibrate --scale_ambiguous=3 data/3.txt data/2.txt data/1.txt
Note that the scale ambiguous motions are provided in the third argument (--scale_ambiguous=3), which is data/1.txt and NOT the file with name 3.txt. The wheel and laser motions are considered metrically accurate (2.txt and 3.txt, respectively).
The output are the Sim(2) extrinsic calibration of each sensor with respect to the reference sensor (omitted). The output format is:
x, y, yaw, scale
The angle is expressed in radians. To recover the metrically accurate translation, just multiply the scale factor and the 2D translation vector.