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ouster-lidar / ouster-sdk

Ouster, Inc. sample code
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Need help understanding /os1_node/lidar_packets messages #73

Closed Justgo13 closed 4 years ago

Justgo13 commented 5 years ago

I currently have a .bag file from recording with the OS1 lidar and I am using ROS melodic on Ubuntu 18.04. Can someone help me understand the numbers in the messages that are being outputted under my topics '/os1_node/imu_packets' and '/os1_node/lidar_packets'.

Update: Wrote lidar data to csv file so better visualization test.zip

zuzi-m commented 5 years ago

The data in the topics is in a form of ROS messages that just wrap the original data from the OS1 sensor in binary format. It is exactly the same data that comes from OS-1 sensor over the network in UDP packets. The format is documented in the software guide, section 3.4 Lidar Data Format and 3.5 IMU Data Format

To decode the data you can implement an ROS node that subscribes to these topics and uses the ouster_client library to read the data. An example of a node doing this is the os1_cloud_node here in this repository.

mrgransky commented 4 years ago

How about this workaround to get all the topics directly than writing ROS node:

  1. Bring up OS1: $ roslaunch ouster_ros os1.launch os1_hostname:=os1-xxxxxxxxxxxx.local udp_add:=X.X.X.X lidar_mode:=2048x10 image:=true

  2. Record my_file.bag $ rosbag record -a -O my_file

  3. Show info: $ rosbag info my_file.bag --freq

path:        my_file.bag
version:     2.0
duration:    30.0s
start:       Jan 08 2020 19:55:54.42 (1578506154.42)
end:         Jan 08 2020 19:56:24.37 (1578506184.37)
size:        2.3 GB            <<<<<<<<<---------------------- My only problem 
messages:    45238
compression: none [894/894 chunks]
types:       ouster_ros/PacketMsg    [4f7b5949e76f86d01e96b0e33ba9b5e3]
             rosgraph_msgs/Log       [acffd30cd6b6de30f120938c17c593fb]
             sensor_msgs/Image       [060021388200f6f0f447d0fcd9c64743]
             sensor_msgs/Imu         [6a62c6daae103f4ff57a132d6f95cec2]
             sensor_msgs/PointCloud2 [1158d486dd51d683ce2f1be655c3c181]
             tf2_msgs/TFMessage      [94810edda583a504dfda3829e70d7eec]
topics:      /img_node/intensity_image     297 msgs @  10.0 Hz : sensor_msgs/Image      
             /img_node/noise_image         297 msgs @  10.0 Hz : sensor_msgs/Image      
             /img_node/range_image         297 msgs @  10.0 Hz : sensor_msgs/Image      
             /os1_cloud_node/imu          2978 msgs @ 100.3 Hz : sensor_msgs/Imu        
             /os1_cloud_node/points        298 msgs @   9.9 Hz : sensor_msgs/PointCloud2
             /os1_node/imu_packets        2978 msgs @ 100.1 Hz : ouster_ros/PacketMsg   
             /os1_node/lidar_packets     38083 msgs @ 41.5 kHz : ouster_ros/PacketMsg   
             /rosout                         9 msgs @ 25.0 kHz : rosgraph_msgs/Log       (3 connections)
             /tf_static                      1 msg             : tf2_msgs/TFMessage

As you can see, all topics are there, but the size of the bag file is dramatically large for a 30 sec ride :( Is there any alternative to address this problem?