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Introduction

Caesar is a modern robotic framework for localization and mapping, reducing the barrier of entry for Simultaneous Localization and Mapping (SLAM). Caesar attempts to address a number of issues that arise in prior SLAM solutions - solving under-defined systems, inference with non-Gaussian measurements, simplifying factor creation, and centralizing factor-graph persistence with databases and cloud infrastructure. Caesar started as part of reseach work in navigation systems and direct the reader to the literature reference page for more information.

Focus Area

This project focuses on the open development and progression to a public, stable, growing and usable inference library suited to various data-fusion / state-estimation aspects of robot and/or device navigation.

The Caesar Framework

Caesar.jl is the "umbrella" framework for other dedicated algorithmic/supporting packages that are implemented in Julia (and JuliaPro). A few packages are wrapped C libraries, which can be incorporated with zero overhead, such as AprilTags.jl.

FAQ: Why use Julia?

RoME.jl/IncrementalInference.jl/ApproxManifoldProducts.jl

Critically, this package can operate in the conventional SLAM manner, using local memory (dictionaries), or alternatively distribute around a persisted FactorGraph through a graph database using CloudGraphs.jl, as discussed in literature here [1.3]. A variety of plotting, 3D visualization, serialization, LCM middleware, and analysis tools come standard. Please see internal packages, Robot Motion Estimate RoME.jl and back-end solver IncrementalInference.jl.

Details about the accompanying packages:

  • IncrementalInference.jl supplies the algebraic logic for factor graph inference with Bayes tree and depends on several packages itself.
  • RoME.jl introduces nodes and factors that are useful to robotic navigation.

Visualization (Arena.jl/RoMEPlotting.jl)

Caesar visualization (plotting of results, graphs, and data) is provided by 2D and 3D packages respectively:

  • RoMEPlotting.jl are a set of scripts that provide MATLAB style plotting of factor graph beliefs, mostly supporting 2D visualization with some support for projections of 3D;
  • Arena.jl package, which is a collection of 3D visualization tools.

Multilanguage Interops: Caesar SDKs and APIs

The Caesar framework is not limited to direct Julia use. See the multi-language page for details.

FAQ: Interop with other languages (not limited to Julia only)

A Few Highlights

Updates to this list coming soon

The Caesar framework has the following features:

  • Distributed Factor Graph representation of pose and sensor data
  • Localization using Multi-modal iSAM
    • Multi-core inference supporting Pose2, Pose3, Point2, Point3, Multi-modal (multi-hypothesis), IMU preintegration, KDE density, intensity map, partial constraints, null hypothesis, etc
  • Multi-modal and non-parametric representation of constraints
    • Gaussian distributions are but one of the many representations of measurement error
    • Simple, extensible framework for creation of new factor types
  • Multi-hypothesis representation in the factor-graph
  • Local in-memory solving on the device as well as database-driven centralized solving (micro-service architecture).
  • Fixed-lag, continuous operation as well as off-line batch solving

Origins in Fundamental Research

See related works on the literature page. Many future directions are in the works – including fundamental research, implementation quality/performance, and system integration. Please see/open issues for specific requests or adding comments to an ongoing discussion – also consult the Caesar.jl Slack channel to follow/engage with community discussions.

Note

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Next Steps

For installation steps, examples/tutorials, and concepts please refer to the following pages:

Please file issues here as needed to help resolve problems for everyone! We are tracking improvements and new endeavors on the Issues page of this repository – issues frequently are moved upstream into each of the indivisual library packages, while Caesar.jl frequently acts as a catchall to help get problems resolved.

JuliaRobotics Code of Conduct

The Caesar repository is part of the JuliaRobotics organization and adheres to the JuliaRobotics code-of-conduct.

Contributors

We are grateful for many, many contributions within the Julia package ecosystem – see the REQUIRE files of Caesar, Arena, RoME, RoMEPlotting, KernelDensityEstimate, IncrementalInference, NLsolve, DrakeVisualizer, Graphs, CloudGraphs and others for a far reaching list of contributions.

Consider citing our work:

@misc{caesarjl,
  author = "Contributors and Packages",
  title =  "Caesar.jl",
  year =   2020,
  url =    "https://github.com/JuliaRobotics/Caesar.jl"
}

Administration of the Caesar/RoME/IncrementalInference/Arena packages is currently conducted by Dehann Fourie who can be contacted for more details.