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The official repository of our ICRA 2024 paper "Stereo-NEC: Enhancing Stereo Visual-Inertial SLAM Initialization with Normal Epipolar Constraints".

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ORB-SLAM3 with Stereo-NEC

Project Overview

Stereo-NEC aims to improve the initialization accuracy and robustness of stereo VI-SLAM systems. We release a version of the code with features integrated into ORB-SLAM3 to demonstrate the concept. However, the comprehensive code version used in our proprietary SLAM system, intended for product use, will not be released.

Features included in this repository:

  • Gyroscope Bias Estimator
  • IMU-only Optimization
  • 3-DoF Bundle Adjustment for enhancing translation
  • Joint Visual-Inertial Bundle Adjustment

Tested on Ubuntu 20.04 and 22.04.

Relative Rotation Error (RRE) for different methods with different number of keyframes.

Left: Results with 5 and 10 keyframes without VI-BA for initialization. Right: Results with 5 and 10 keyframes with VI-BA applied for initialization.

Improve rotation estimation of a visual-inertial system by:

Utilizing normal epipolar constraints to estimate initial gyroscope bias and uses it to initialize a maximum a posteriori (MAP) problem for further refinement and estimate inertial parameters.

Enhance translation estimation of a visual-inertial system by:

Separately estimating rotation using IMU integration and leverage precise rotation estimates to enhance translation estimation via 3-DoF bundle adjustment.

1. Prepare the EuRoC Dataset

EuRoC dataset was recorded with two pinhole cameras and an inertial sensor.

Download a sequence in ASL format by running the script we provided:

chmod +x scripts/download_euroc_dataset.sh
./scripts/download_euroc_dataset.sh

2. Install Ceres (version 1.14.0)

Start by installing all the dependencies:

# CMake
sudo apt-get install cmake
# google-glog + gflags
sudo apt-get install libgoogle-glog-dev libgflags-dev
# Use ATLAS for BLAS & LAPACK
sudo apt-get install libatlas-base-dev
# Eigen3
sudo apt-get install libeigen3-dev
# SuiteSparse (optional)
sudo apt-get install libsuitesparse-dev

Download the source code, compile it, and install:

git clone https://ceres-solver.googlesource.com/ceres-solver
cd ceres-solver
git checkout 1.14.0
mkdir build
mkdir -p build && cd build
cmake -DCMAKE_BUILD_TYPE=Release ..
make -j$(nproc)
sudo make install

3. Install OpenCV 4

Tested with OpenCV versions 4.2.0, 4.6.0, and 4.7.0 on Ubuntu 20.04 and Ubuntu 22.04.

4. Running Stereo-Inertial:

Create a separate folder to store results for each sequence.

mkdir -p results/XXXX 

Replace 'XXXX' with one value from the list: (MH01, MH02, MH03, MH04, MH05, V101, V102, V103, V201, V202, V203)

Compile the source code and run it:

./build.sh
./Examples/Stereo-Inertial/stereo_inertial_euroc Vocabulary/ORBvoc.txt Examples/Stereo-Inertial/EuRoC.yaml PATH_TO_EuRoC_DATASET/XXX
Examples/Stereo-Inertial/EuRoC_TimeStamps/XXXX.txt 
# Ensure the results from each sequence are moved to the corresponding folder
mv results/*.csv results/XXXX

Example of running the sequence V203:

mkdir -p results/V203
./Examples/Stereo-Inertial/stereo_inertial_euroc Vocabulary/ORBvoc.txt Examples/Stereo-Inertial/EuRoC.yaml Dataset/EuRoC/V2_03_difficult Examples/Stereo-Inertial/EuRoC_TimeStamps/V203.txt 
# Ensure the results from V203 are moved to the V203 folder
mv results/*.csv results/V203

5. Evaluation

To process the sequences and calculate the ATE and RRE, run the script provided:

conda create -n "evo_env"
conda activate evo_env
[evo_env] pip install evo --upgrade --no-binary evo
[evo_env] pip install pandas
[evo_env] pip install tqdm
[evo_env] python3 scripts/test_euroc.py --est_folder_path=$EST_PATH_TO_RESULTS --gt=PATH_TO_EuRoC_DATASET/XXX/mav0/state_groundtruth_estimate0/data.csv

Example:

python3 scripts/test_euroc.py --est_folder_path=results/V203/ --gt=Dataset/EuRoC/V2_03_difficult/mav0/state_groundtruth_estimate0/data.csv

If you want to evaluate all sequences, we also provide a script for that purpose:

./scripts/evaluate_init_euroc.sh

ORB-SLAM3

V1.0, December 22th, 2021

Authors: Carlos Campos, Richard Elvira, Juan J. Gómez Rodríguez, José M. M. Montiel, Juan D. Tardos.

The Changelog describes the features of each version.

ORB-SLAM3 is the first real-time SLAM library able to perform Visual, Visual-Inertial and Multi-Map SLAM with monocular, stereo and RGB-D cameras, using pin-hole and fisheye lens models. In all sensor configurations, ORB-SLAM3 is as robust as the best systems available in the literature, and significantly more accurate.

We provide examples to run ORB-SLAM3 in the EuRoC dataset using stereo or monocular, with or without IMU, and in the TUM-VI dataset using fisheye stereo or monocular, with or without IMU. Videos of some example executions can be found at ORB-SLAM3 channel.

This software is based on ORB-SLAM2 developed by Raul Mur-Artal, Juan D. Tardos, J. M. M. Montiel and Dorian Galvez-Lopez (DBoW2).

ORB-SLAM3

Related Publications:

[ORB-SLAM3] Carlos Campos, Richard Elvira, Juan J. Gómez Rodríguez, José M. M. Montiel and Juan D. Tardós, ORB-SLAM3: An Accurate Open-Source Library for Visual, Visual-Inertial and Multi-Map SLAM, IEEE Transactions on Robotics 37(6):1874-1890, Dec. 2021. PDF.

[IMU-Initialization] Carlos Campos, J. M. M. Montiel and Juan D. Tardós, Inertial-Only Optimization for Visual-Inertial Initialization, ICRA 2020. PDF

[ORBSLAM-Atlas] Richard Elvira, J. M. M. Montiel and Juan D. Tardós, ORBSLAM-Atlas: a robust and accurate multi-map system, IROS 2019. PDF.

[ORBSLAM-VI] Raúl Mur-Artal, and Juan D. Tardós, Visual-inertial monocular SLAM with map reuse, IEEE Robotics and Automation Letters, vol. 2 no. 2, pp. 796-803, 2017. PDF.

[Stereo and RGB-D] Raúl Mur-Artal and Juan D. Tardós. ORB-SLAM2: an Open-Source SLAM System for Monocular, Stereo and RGB-D Cameras. IEEE Transactions on Robotics, vol. 33, no. 5, pp. 1255-1262, 2017. PDF.

[Monocular] Raúl Mur-Artal, José M. M. Montiel and Juan D. Tardós. ORB-SLAM: A Versatile and Accurate Monocular SLAM System. IEEE Transactions on Robotics, vol. 31, no. 5, pp. 1147-1163, 2015. (2015 IEEE Transactions on Robotics Best Paper Award). PDF.

[DBoW2 Place Recognition] Dorian Gálvez-López and Juan D. Tardós. Bags of Binary Words for Fast Place Recognition in Image Sequences. IEEE Transactions on Robotics, vol. 28, no. 5, pp. 1188-1197, 2012. PDF

1. License

ORB-SLAM3 is released under GPLv3 license. For a list of all code/library dependencies (and associated licenses), please see Dependencies.md.

For a closed-source version of ORB-SLAM3 for commercial purposes, please contact the authors: orbslam (at) unizar (dot) es.

If you use ORB-SLAM3 in an academic work, please cite:

@article{ORBSLAM3_TRO,
  title={{ORB-SLAM3}: An Accurate Open-Source Library for Visual, Visual-Inertial 
           and Multi-Map {SLAM}},
  author={Campos, Carlos AND Elvira, Richard AND G\´omez, Juan J. AND Montiel, 
          Jos\'e M. M. AND Tard\'os, Juan D.},
  journal={IEEE Transactions on Robotics}, 
  volume={37},
  number={6},
  pages={1874-1890},
  year={2021}
 }

2. Prerequisites

We have tested the library in Ubuntu 16.04 and 18.04, but it should be easy to compile in other platforms. A powerful computer (e.g. i7) will ensure real-time performance and provide more stable and accurate results.

C++11 or C++0x Compiler

We use the new thread and chrono functionalities of C++11.

Pangolin

We use Pangolin for visualization and user interface. Dowload and install instructions can be found at: https://github.com/stevenlovegrove/Pangolin.

OpenCV

We use OpenCV to manipulate images and features. Dowload and install instructions can be found at: http://opencv.org. Required at leat 3.0. Tested with OpenCV 3.2.0 and 4.4.0.

Eigen3

Required by g2o (see below). Download and install instructions can be found at: http://eigen.tuxfamily.org. Required at least 3.1.0.

DBoW2 and g2o (Included in Thirdparty folder)

We use modified versions of the DBoW2 library to perform place recognition and g2o library to perform non-linear optimizations. Both modified libraries (which are BSD) are included in the Thirdparty folder.

Python

Required to calculate the alignment of the trajectory with the ground truth. Required Numpy module.

ROS (optional)

We provide some examples to process input of a monocular, monocular-inertial, stereo, stereo-inertial or RGB-D camera using ROS. Building these examples is optional. These have been tested with ROS Melodic under Ubuntu 18.04.

3. Building ORB-SLAM3 library and examples

Clone the repository:

git clone https://github.com/UZ-SLAMLab/ORB_SLAM3.git ORB_SLAM3

We provide a script build.sh to build the Thirdparty libraries and ORB-SLAM3. Please make sure you have installed all required dependencies (see section 2). Execute:

cd ORB_SLAM3
chmod +x build.sh
./build.sh

This will create libORB_SLAM3.so at lib folder and the executables in Examples folder.

4. Running ORB-SLAM3 with your camera

Directory Examples contains several demo programs and calibration files to run ORB-SLAM3 in all sensor configurations with Intel Realsense cameras T265 and D435i. The steps needed to use your own camera are:

  1. Calibrate your camera following Calibration_Tutorial.pdf and write your calibration file your_camera.yaml

  2. Modify one of the provided demos to suit your specific camera model, and build it

  3. Connect the camera to your computer using USB3 or the appropriate interface

  4. Run ORB-SLAM3. For example, for our D435i camera, we would execute:

./Examples/Stereo-Inertial/stereo_inertial_realsense_D435i Vocabulary/ORBvoc.txt ./Examples/Stereo-Inertial/RealSense_D435i.yaml

5. EuRoC Examples

EuRoC dataset was recorded with two pinhole cameras and an inertial sensor. We provide an example script to launch EuRoC sequences in all the sensor configurations.

  1. Download a sequence (ASL format) from http://projects.asl.ethz.ch/datasets/doku.php?id=kmavvisualinertialdatasets

  2. Open the script "euroc_examples.sh" in the root of the project. Change pathDatasetEuroc variable to point to the directory where the dataset has been uncompressed.

  3. Execute the following script to process all the sequences with all sensor configurations:

./euroc_examples

Evaluation

EuRoC provides ground truth for each sequence in the IMU body reference. As pure visual executions report trajectories centered in the left camera, we provide in the "evaluation" folder the transformation of the ground truth to the left camera reference. Visual-inertial trajectories use the ground truth from the dataset.

Execute the following script to process sequences and compute the RMS ATE:

./euroc_eval_examples

6. TUM-VI Examples

TUM-VI dataset was recorded with two fisheye cameras and an inertial sensor.

  1. Download a sequence from https://vision.in.tum.de/data/datasets/visual-inertial-dataset and uncompress it.

  2. Open the script "tum_vi_examples.sh" in the root of the project. Change pathDatasetTUM_VI variable to point to the directory where the dataset has been uncompressed.

  3. Execute the following script to process all the sequences with all sensor configurations:

./tum_vi_examples

Evaluation

In TUM-VI ground truth is only available in the room where all sequences start and end. As a result the error measures the drift at the end of the sequence.

Execute the following script to process sequences and compute the RMS ATE:

./tum_vi_eval_examples

7. ROS Examples

Building the nodes for mono, mono-inertial, stereo, stereo-inertial and RGB-D

Tested with ROS Melodic and ubuntu 18.04.

  1. Add the path including Examples/ROS/ORB_SLAM3 to the ROS_PACKAGE_PATH environment variable. Open .bashrc file:
gedit ~/.bashrc

and add at the end the following line. Replace PATH by the folder where you cloned ORB_SLAM3:

export ROS_PACKAGE_PATH=${ROS_PACKAGE_PATH}:PATH/ORB_SLAM3/Examples/ROS
  1. Execute build_ros.sh script:
chmod +x build_ros.sh
./build_ros.sh

Running Monocular Node

For a monocular input from topic /camera/image_raw run node ORB_SLAM3/Mono. You will need to provide the vocabulary file and a settings file. See the monocular examples above.

rosrun ORB_SLAM3 Mono PATH_TO_VOCABULARY PATH_TO_SETTINGS_FILE

Running Monocular-Inertial Node

For a monocular input from topic /camera/image_raw and an inertial input from topic /imu, run node ORB_SLAM3/Mono_Inertial. Setting the optional third argument to true will apply CLAHE equalization to images (Mainly for TUM-VI dataset).

rosrun ORB_SLAM3 Mono PATH_TO_VOCABULARY PATH_TO_SETTINGS_FILE [EQUALIZATION]	

Running Stereo Node

For a stereo input from topic /camera/left/image_raw and /camera/right/image_raw run node ORB_SLAM3/Stereo. You will need to provide the vocabulary file and a settings file. For Pinhole camera model, if you provide rectification matrices (see Examples/Stereo/EuRoC.yaml example), the node will recitify the images online, otherwise images must be pre-rectified. For FishEye camera model, rectification is not required since system works with original images:

rosrun ORB_SLAM3 Stereo PATH_TO_VOCABULARY PATH_TO_SETTINGS_FILE ONLINE_RECTIFICATION

Running Stereo-Inertial Node

For a stereo input from topics /camera/left/image_raw and /camera/right/image_raw, and an inertial input from topic /imu, run node ORB_SLAM3/Stereo_Inertial. You will need to provide the vocabulary file and a settings file, including rectification matrices if required in a similar way to Stereo case:

rosrun ORB_SLAM3 Stereo_Inertial PATH_TO_VOCABULARY PATH_TO_SETTINGS_FILE ONLINE_RECTIFICATION [EQUALIZATION]	

Running RGB_D Node

For an RGB-D input from topics /camera/rgb/image_raw and /camera/depth_registered/image_raw, run node ORB_SLAM3/RGBD. You will need to provide the vocabulary file and a settings file. See the RGB-D example above.

rosrun ORB_SLAM3 RGBD PATH_TO_VOCABULARY PATH_TO_SETTINGS_FILE

Running ROS example: Download a rosbag (e.g. V1_02_medium.bag) from the EuRoC dataset (http://projects.asl.ethz.ch/datasets/doku.php?id=kmavvisualinertialdatasets). Open 3 tabs on the terminal and run the following command at each tab for a Stereo-Inertial configuration:

roscore
rosrun ORB_SLAM3 Stereo_Inertial Vocabulary/ORBvoc.txt Examples/Stereo-Inertial/EuRoC.yaml true
rosbag play --pause V1_02_medium.bag /cam0/image_raw:=/camera/left/image_raw /cam1/image_raw:=/camera/right/image_raw /imu0:=/imu

Once ORB-SLAM3 has loaded the vocabulary, press space in the rosbag tab.

Remark: For rosbags from TUM-VI dataset, some play issue may appear due to chunk size. One possible solution is to rebag them with the default chunk size, for example:

rosrun rosbag fastrebag.py dataset-room1_512_16.bag dataset-room1_512_16_small_chunks.bag

8. Running time analysis

A flag in include\Config.h activates time measurements. It is necessary to uncomment the line #define REGISTER_TIMES to obtain the time stats of one execution which is shown at the terminal and stored in a text file(ExecTimeMean.txt).

9. Calibration

You can find a tutorial for visual-inertial calibration and a detailed description of the contents of valid configuration files at Calibration_Tutorial.pdf

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The official repository of our ICRA 2024 paper "Stereo-NEC: Enhancing Stereo Visual-Inertial SLAM Initialization with Normal Epipolar Constraints".

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