ros2gams

ros2gams

ros2gams is a tool which converts rosbag files to madara checkpoints. The tool will create a checkpoint with each ROS message in the rosbag (default). It is also possible to create checkpoints with a given frequency (see option -y). The conversion process is defined in a mapfile which assigns a madara variable name to each rostopic.

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Commandline arguments

  [-r|--rosbag file]                   Path to the rosbag file
  [-scp|--save-checkpoint-prefix prfx] prefix of knowledge to save in checkpoint
  [-sb|--save-binary]                  save the resulting knowledge base as a binary checkpoint
  [-sk|--save-karl]                    save the resulting knowledge base as a karl checkpoint
  [-sj|--save-json]                    save the resulting knowledge base as a json checkpoint
  [-m|--map-file file]                 File with filter and mapping information
  [-y|--frequency hz]                  Checkpoint frequency (default: checkpoint with each message in the bagfile [= checkpoint with each lamportclock tick])

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Output format

ros2gams supports three output formats - binary, karl and json. It is possible to convert to a single or multiple formats in one run. Simply add the corresponding commandline arguments (-sb, -sk, -sj). If no output format is specified the file is stored in the karl-format by default.

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Mapfile

The mapfile defines the conversion process and selects the topics which should be converted. Here is an example mapfile:

frames:
  base_frame: p1/base_link
  world_frame: geo

topics:
  mavros/local/pose:
    name: .sensors.px4.location
    circular_buffer_size: 10

capnp_schemas:
  - $(GAMS_ROOT)/tests/capnfiles/Odometry.capnp.bin
  - $(GAMS_ROOT)/tests/capnfiles/PoseStamped.capnp.bin

schema_map:
  nav_msgs/Odometry: tests/capnfiles/Odometry.capnp:Odometry
  geometry_msgs/Point: tests/capnfiles/Point.capnp:Point
  geometry_msgs/PoseStamped: tests/capnfiles/PoseStamped.capnp:PoseStamped

Agent position and orientation

To calculate the agent's position and orientation it is necessary to define the base_frame and world_frame in the frames namespace.

Topics

The topics namespace defines all ROS topics which will be selected for conversion. The keys of the topics dictionary are the ROS names. Each element needs to have at least a name member which defines the Madara variable name. The value circular_buffer_size is optional and defines if this variable has to be stored in a CircularBuffer and the size of this buffer. The example from above converts the ROS topic mavros/local/pose to the variable .sensors.px4.location. This variable uses a CircularBuffer with a buffersize of 10 elements. The minimal setup for a variable mapping is defined as:

ros_name:
    name: madara_name

Capnproto Schemas

ROS topics can be mapped to capnproto schemas. To provide ros2gams with the schemas the necessary files can be defined in capnschemas. These files are loaded and all the schemas and underlying subschemas are available during the parsing.

Schema Map

The schema map defines which ROS message types are mapped to capnproto schemas and stored in Any types. The example configuration from above results in checkpoints with all Odometry, Point and PoseStamped messages mapped to capnproto schemas. Please keep in mind that all messages with the specified type will be mapped to the capnproto schema defined in this map.

Name Substitutions

To change the name of ros topic type members you are able to specify this in a type-specific mapping. Example:

name_substitution:
  sensor_msgs/LaserScan:
    /angle_min: /a_min
    /angle_max: /a_max

This example would result in the members /angle_min and /angle_max to be renamed to /a_min and /a_max.

TOI

If you want to use the ros receive time as toi instead of the current madara time you have to compile with the simtime parameter enabled. This means you have to build by calling: ./scripts/linux/base_build.sh ros gams madara simtime

Known limitations

• Topic types which are non ROS standard types are converted via topic introspection. Due to limitations in this process the size of arrays for these types is limited to 100 elements. This may change in future.
• Only capnproto Any elements can be stored in CircularBuffers
• Name substitution works only for Any types
• Capnproto schemas need to be in the binary format