2018-01-02:The PCD (Point Cloud Data) file format

The pcd file format are as below, this is a generated pcd file format:

# .PCD v0.7 - Point Cloud Data file format
VERSION 0.7
FIELDS x y z
SIZE 4 4 4
TYPE F F F
COUNT 1 1 1
WIDTH 5
HEIGHT 1
VIEWPOINT 0 0 0 1 0 0 0
POINTS 5
DATA ascii
0.35222197 -0.15188313 -0.10639524
-0.3974061 -0.47310591 0.29260206
-0.73189831 0.66710472 0.44130373
-0.73476553 0.85458088 -0.036173344
-0.46070004 -0.2774682 -0.91676188

Now, let’s break down it piece by piece.
1. The first part:

# .PCD v0.7 - Point Cloud Data file format

This line shows that pcd file format in PCL library should be version 0.7

2. The second part:

VERSION 0.7
FIELDS x y z
SIZE 4 4 4
TYPE F F F
COUNT 1 1 1
WIDTH 5
HEIGHT 1
VIEWPOINT 0 0 0 1 0 0 0
POINTS 5
DATA ascii

Each PCD file contains a header that identifies and declares certain properties of the point cloud data stored in the file. The header of a PCD must be encoded in ASCII.
VERSION:specifies the PCD file version
FIELDS:specifies the name of each dimension/field that a point can have
SIZE:specifies the size of each dimension in bytes
TYPE:specifies the type of each dimension by I or U or F
COUNT:specifies how many elements does each dimension have, if COUNT is not present, all dimensions’ count is set to 1
WIDTH:specifies the width of the point cloud dataset in the number of points. WIDTH has two meanings.

it can specify the total number of points in the cloud (equal with POINTS) for unorganized datasets;
it can specify the width (total number of points in a row) of an organized point cloud dataset.

HEIGHT:specifies the height of the point cloud dataset in the number of points. HEIGHT has two meanings.

it can specify the height (total number of rows) of an organized point cloud dataset;
it is set to 1 for unorganized datasets (thus used to check whether a dataset is organized or not).

VIEWPOINT:specifies an acquisition viewpoint for the points in the dataset. The viewpoint information is specified as a translation (tx ty tz) + quaternion (qw qx qy qz). The default value is:

VIEWPOINT 0 0 0 1 0 0 0

POINTS:specifies the total number of points in the cloud.As of version 0.7, its purpose is a bit redundant, so we’re expecting this to be removed in future versions.
DATA:specifies the data type that the point cloud data is stored in. As of version 0.7, two data types are supported: ascii and binary.

3. The third part:

0.35222197 -0.15188313 -0.10639524
-0.3974061 -0.47310591 0.29260206
-0.73189831 0.66710472 0.44130373
-0.73476553 0.85458088 -0.036173344
-0.46070004 -0.2774682 -0.91676188

As of version 0.7, the .PCD file format uses two different modes for storing data:

in ASCII form, with each point on a new line:

p_1
p_2
p_3
p_4
...
p_n

in binary form, where the data is a complete memory copy of the pcl::PointCloud.points array or vector. On Linux systems, we use mmap or munmap operations for the fastest possible read/write access to the data.

最后编辑于：2018.01.02 16:55:10