sensor_filters

This package is a collection of nodes and nodelets that service a filters::FilterChain for message types from sensor_msgs package.

Each node/nodelet's task is very simple: load the filter chain, subscribe ~input topic, and publish the filtered messages to ~output topic.

The size of message queues is configured via ~input_queue_size and ~output_queue_size, both defaulting to 10 messages.

The namespaces from which the filters load are the following:

Provided filters

sensor_filters/ChangeHeader/$MESSAGE_TYPE

This filter allows changing the contents of the header of sensor messages. You can use it for example to correct the frame_id of a sensor, or the adjust the timestamp of its messages.

Parameters

• frame_id_prefix (string): Add this prefix to header.frame_id
• frame_id_suffix (string): Add this suffix to header.frame_id
• frame_id (string): Replace header.frame_idwith this value (prefix and suffix are then ignored)
• seq (uint): Replace header.seq with this value
• seq_relative (uint): Add this value to header.seq (watch out for unsigned int underflow)
• stamp (double): Set header.stamp to this value (double value is converted to ros::Time)
• stamp_relative (double): Add this value to header.stamp (double value is converted to ros::Duration)

laser_filters compatibility

The LaserScan filter chain node is compatible with the scan_to_scan_node from laser_filters package (it can load the same filters using the same config). It does not, however, use TF message filter, so each filter has to wait for the required TFs itself.

Extensibility

Both the nodes and nodelets offer common code that can be shared so that you can build extensions of the simple filter chain handlers provided by this package.

Nodes

#include <sensor_msgs/PointCloud2.h>
#include <sensor_filters/FilterChainNode.h>

class MyClass : public sensor_filters::FilterChainNode<sensor_msgs::PointCloud2>
{
  // custom class code
};

Nodelets

#include <pluginlib/class_list_macros.h>
#include <sensor_msgs/PointCloud2.h>
#include <sensor_filters/FilterChainNodelet.h>

class MyNodelet : public sensor_filters::FilterChainNodelet<sensor_msgs::PointCloud2>
{
  protected: void onInit() override
  {
    sensor_filters::FilterChainNodelet<sensor_msgs::PointCloud2>::onInit();
    // custom nodelet code
  }
};

PLUGINLIB_EXPORT_CLASS(MyNodelet, nodelet::Nodelet)

Example

filter.yaml

output_queue_size: 1
scan_filter_chain:
  - name: intensity
    type: laser_filters/LaserScanIntensityFilter
    params:
      lower_threshold: 8000
      upper_threshold: 100000
      invert: false
      filter_override_range: true
      filter_override_intensity: false
  - name: shadows
    type: laser_filters/ScanShadowsFilter
    params:
      min_angle: 10
      max_angle: 170
      neighbors: 20
      window: 0

filter.launch

<launch>
    <node pkg="sensor_filters" type="laserscan_filter_chain" output="screen" name="laser_filter">
        <remap from="~input" to="base_scan" />
        <remap from="~output" to="base_scan_filtered" />
        <rosparam command="load" file="$(dirname)/filter.yaml" />
    </node>
</launch>