SLAM system YAML configuration file format

Refer to demos for real examples to launch and run SLAM systems.

File structure

A SLAM system is defined via a YAML configuration file, comprising a top-level modules entry, with one or more children elements with the following required fields:

# my-slam-system.yml
modules:
  - type: CLASS_NAME1       # mandatory
    name: INSTANCE_NAME1    # mandatory
    execution_rate: 20      # Hz (optional)
    verbosity_level: INFO   # DEBUG|INFO|WARN|ERROR
    params:                 # Other module-specific parameters
      var1: value1
      var2: value2
      # ...
  - type: CLASS_NAME2
    name: INSTANCE_NAME2
  # ...

Notes:

• CLASS_NAME1: The C++ class name of one of the modules registered in the MOLA system.

• INSTANCE_NAME1: Arbitrary name of this instance of the module. All names must be unique in a SLAM system.

YAML extensions

MOLA supports the following extensions to standard YAML to ease the maintenance of configuration files:

Include other files: $include{xxx}

The contents of any entry with the syntax $include{/path/to/other/file.yml} will be replaced by the actual contents of the given file, which should be given in either absolute path, or relative to the current YAML file being parsed.

modules:
  - type: CLASS_NAME1       # mandatory
    #...
    params:                 # Other module-specific parameters
      $include{$(ros2 pkg prefix mola_lidar_odometry)/share/xxx/xxxx.yaml}
    config:
      $include{params/xxxx.yaml}

Replace environment variables: ${foo}

If any YAML content contains the pattern ${foo}, it is replaced by the current value of the given environment variable. A fatal error is raised if the variable is not defined.

Replace output of external process: $(cmd)

The pattern $(cmd arg1 arg2...) is replaced by the console output of running the given command with the given arguments. See for example its usage together with $include{xxx} above.

Mathematical formulas : $f{xxx}

The pattern $f{expr} can be used to indicate mathematical expressions. The ExprTk library is used (via mrpt-expr), so refer to their documentation for built-in functions and syntax. User-defined variables can be used, depending on the context of the YAML file being parsed.