Clarify data[] in PointCloud2 message [closed]

asked 2022-04-29 01:29:39 -0500

Petros ADLATUS gravatar image

updated 2022-05-20 00:56:27 -0500

Hello folks,

I have a question about the interpretation of my point cloud data. Actually, everything is clear to me, but I don't really understand the values in data[] itself. I have understood that these numbers are represented in 4 byte values (uint8 FLOAT32 = 7), so for example 128 = 00000000 00000000 00000000 10000000.

example snippet: [128, 63, 188, 116, 147, 65, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 128, 63, 80, 141, 151, 65]

he question is what every 4 values represent:

   x = 128
    y = 63
    z = 188
    intensity = 116

or am I wrong and x = 128,63,188,116.

++++++++++++++++++++++

Additional question: Thank you both, I could get the information I've searched. Only one thing, if its mentioned, that the bytes are stored in little endian. It must be stored like this 128,63,188,116 for x:

memory a: 128 a+1: 63 a+2: 188 a+3: 116

or will it be stored from the right side beginning, so:

memory a: 116 a+1: 188 a+2: 63 a+3: 128

Thank you for every discussion.

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Closed for the following reason duplicate question by gvdhoorn
close date 2022-04-29 02:22:03.509141

Comments

1

Can't directly answer but there are some link hopefuly explain what you are looking for. Hope it helps!

what-is-the-definition-of-the-contents-of-pointcloud2

pcl/Overview

sensor_msgs/PointCloud2

FurkanEdizkan gravatar image FurkanEdizkan  ( 2022-04-29 01:40:07 -0500 )edit

I've closed this as a duplicate, as there are a number of previously asked (and answered) Q&As which seem to discuss the same topic: see #q273182, #q373094, #q300906, #q349814, #q319350 and #q294913 for instance.

There are many more. A google search with site:answers.ros.org should return them.

@Petros ADLATUS: if those do not answer your question, please edit your current question and clarify what exactly is (still) unclear.

gvdhoorn gravatar image gvdhoorn  ( 2022-04-29 02:24:53 -0500 )edit