1.The LaserScan Message

   、ROS 中提供了一种很特殊的  Message type 在sensor-MSG  包当中，他是LaserScan ，他使得编码已获得的信息变得极为方便，首先看一下信息的类型。

A：激光扫描的角度是被逆时针测量的

1 Header header 2 float32 angle_min        # start angle of the scan [rad] 3 float32 angle_max        # end angle of the scan [rad] 4 float32 angle_increment  # angular distance between measurements [rad] 5 float32 time_increment   # time between measurements [seconds] 6 float32 scan_time        # time between scans [seconds] 7 float32 range_min        # minimum range value [m] 8 float32 range_max        # maximum range value [m] 9 float32[] ranges         # range data [m] (Note: values < range_min or > range_max should be discarded)10 float32[] intensities    # intensity data [device-specific units]

2. Writing Code to Publish a LaserScan Message

1 #include 
     
       2 #include 
      
          3  4 int main(int argc, char** argv){ 5   ros::init(argc, argv, "laser_scan_publisher"); 6  7   ros::NodeHandle n; 8   ros::Publisher scan_pub = n.advertise
       
        ("scan", 50);  #这是要传递的信息。 9    10   unsigned int num_readings = 100;11   double laser_frequency = 40;12   double ranges[num_readings];13   double intensities[num_readings];  # 准备创建虚拟的激光信息，这分别是平率，不太懂。。。14  15   int count = 0;16   ros::Rate r(1.0);     #发送数据的速率17   while(n.ok()){18     //generate some fake data for our laser scan19     for(unsigned int i = 0; i < num_readings; ++i){20       ranges[i] = count;21       intensities[i] = 100 + count;22     }23     ros::Time scan_time = ros::Time::now();      #每隔一秒产生一个虚假的数据24 25     //populate the LaserScan message26     sensor_msgs::LaserScan scan;27     scan.header.stamp = scan_time;28     scan.header.frame_id = "laser_frame";29     scan.angle_min = -1.57;30     scan.angle_max = 1.57;31     scan.angle_increment = 3.14 / num_readings;32     scan.time_increment = (1 / laser_frequency) / (num_readings);33     scan.range_min = 0.0;34     scan.range_max = 100.0;                   #这些是消息内容。与前一节交相辉映35 36     scan.ranges.resize(num_readings);37     scan.intensities.resize(num_readings);38     for(unsigned int i = 0; i < num_readings; ++i){39       scan.ranges[i] = ranges[i];40       scan.intensities[i] = intensities[i];41     }42 43     scan_pub.publish(scan);44     ++count;45     r.sleep();46   }47 }
       
      
     

3. Publishing PointCloud Message

1 #include 
     
       2 #include 
      
        3  4 int main(int argc, char** argv){ 5   ros::init(argc, argv, "point_cloud_publisher"); 6  7   ros::NodeHandle n; 8   ros::Publisher cloud_pub = n.advertise
       
        ("cloud", 50); 9 10   unsigned int num_points = 100;11 12   int count = 0;13   ros::Rate r(1.0);14   while(n.ok()){15     sensor_msgs::PointCloud cloud;16     cloud.header.stamp = ros::Time::now();17     cloud.header.frame_id = "sensor_frame";18 19     cloud.points.resize(num_points);20 21     //we'll also add an intensity channel to the cloud22     cloud.channels.resize(1);23     cloud.channels[0].name = "intensities";24     cloud.channels[0].values.resize(num_points);25 26     //generate some fake data for our point cloud27     for(unsigned int i = 0; i < num_points; ++i){28       cloud.points[i].x = 1 + count;29       cloud.points[i].y = 2 + count;30       cloud.points[i].z = 3 + count;31       cloud.channels[0].values[i] = 100 + count;32     }33 34     cloud_pub.publish(cloud);35     ++count;36     r.sleep();37   }38 }