How to display real-time 2D map after rviz is opened

1、 background

launch A mapping program , And opened rviz,rviz Also in the add 了 map, however rviz The expected 2D Map , It makes people feel at a loss .

2、 Problem solving

Baidu found that the way it used to build maps was gmapping, It is open source to the famous OpenSLAM Wrapped in ROS An implementation under the framework . This package provides for laser equipment SLAM Support , According to the input of laser equipment and attitude data, a grid based 2D Map . It needs to start from ROS The system monitors many Topic, And output a Topic : /map ,（ The topic data type is nav_msgs/OccupancyGrid）, This is also rviz The input of Topic.

• start-up RViz, Click on add Button ( lower left ) , Select from the list that pops up map, Click on OK, At this time rviz The middle display area is still empty
  
• The most important step , To tell rviz Generate map The information of topic What is it? . We talked about it earlier ,gmapping Output topic yes /map. As shown in the figure below , fill map Of topic, You can immediately see the dynamic establishment of the map