点云数据格式

sensor_msgs/PointCloud2

传感器中用的，像订阅激光点云或者相机点云topic返回的格式

header:            // 点云的头信息
  seq: 963         // 次数
  stamp:           // 时间戳
    secs: 1541143772
    nsecs: 912011000
  frame_id: "/camera_init"
height: 1          // If the cloud is unordered, height is 1
width: 852578      // 点云的长度
fields:            // sensor_msgs/PointField[] fields
  -
    name: "x"
    offset: 0
    datatype: 7          // uint8 INT8    = 1
                         // uint8 UINT8   = 2
                         // uint8 INT16   = 3
                         // uint8 UINT16  = 4
                         // uint8 INT32   = 5
                         // uint8 UINT32  = 6
                         // uint8 FLOAT32 = 7
                         // uint8 FLOAT64 = 8
    count: 1
  -
    name: "y"
    offset: 4
    datatype: 7
    count: 1
  -
    name: "z"
    offset: 8
    datatype: 7
    count: 1
  -
    name: "intensity"
    offset: 16
    datatype: 7
    count: 1
is_bigendian: False
point_step: 32          // Length of a point in bytes
row_step: 27282496      // Length of a row in bytes
data: [ ................... ] // Actual point data, size is (row_step*height)
is_dense: True          // 没有非法数据点

---

pcl::PointT

一般处理点云就要将PointCloud2转为PCL格式，再进行操作

PointT是一类格式，包括PointXYZ、PointXYZI、PointXYZRGBA、PointXYZRGB、PointXY等

看PointXYZI就好了，参考文档

union
{
    float data[4];
    struct
    {
       float x;
       float y;
       float z;
    };
};
union
{
    struct
    {
       float intensity;
     };
    float data_c[4];
};