How to retrieve data from xv-11 lidar using rviz?

edit

Hi,

I suppose that lidar you use provides LaserScan.msg type, which has fields as given in here

for your purpose ,to find points closer than 1m you can use a callback as following;

       YourClass::YourClass(){

          bool red(false),green(false);
          float boundary = 1.0;
          lidar_sub_ = node_handle_ptr_->subscribe("lidar_topic", 1,&YourClass::callback, this);

       }


       void YourClass::callback(const sensor_msgs::LaserScanConstPtr &scan){
          red = false;
          green = true;
          for (int i = 0 ; i < scan->ranges.size(); i++){
            if(scan->ranges[i] < boundary){
              ROS_INFO("A POINT CLOSER THAN BOUNDARY FOUND") ;
              red = true;
              green = false;
              break;
            }
          } 
        }

so after each call your green and red flags will be updated. You can use those flags to do the task you described.