# Tag Info

## Hot answers tagged point-cloud

### What is the definition of the contents of PointCloud2?

I get why you are confused. Looking at the definition of PointCloud2, you see that the field that holds the "actual" point cloud data is a 1-dimensional array. Now,...

### What is the definition of the contents of PointCloud2?

I totally agree that the documentation is poor and it took me quite some time to understand what is going on. I recorded a rosbag for "velodyne_points" topic using a Velodyne VLP-16. The ...
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### 3D mapping using only a 2D Lidar

That is an already solved problem. As Squelsh mentioned CSIRO released its initial version in 2009 and their work is commercialized by GEOSLAM already. One of a CMU student released a open source ...
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### Iterative Closest Point for 2-D LIDAR Data

You can use 3D feature descriptors here to register two point clouds. I've personally used two most recent ones that performed well enough for a similar application. Following are the references to ...
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### ROS PCL: Help with Moving Least Squares filter

Update: I got it working. Thanks for the feedback everyone. To address some of the comments: I wasn't aware that 'filtering' has a specific meaning in the context of PCL. My code wasn't trying to ...
Accepted

### 3D mapping using only a 2D Lidar

I don't think what you're asking is possible with the state of the art sadly. You cannot, AFAIK, generate a 3D map from a hand held 2D LIDAR without any other sensors. It's a very interesting question ...
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### Calculating the distance of a point from point cloud data

These values are relative to the camera. Z is always positive as the camera can't see what is behind. X and Y can be positive or negative depending on if an object is left/right or higher/lower than ...
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### Relation between GraphSLAM and Iterative closest Point algorithm

Iterative closest point is a method to fuse two point clouds together. If Robot A drove around town and gathered some data, then Robot B drove around town and gathered some data, ICP would (...
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### What is the concepts of submaps in LIDAR based graph slam algorithms?

The word is exactly as it sounds. It is a submap of a larger map. Essentially a large map is broken up into smaller submaps in order to improve the computational complexity. In the reference you ...
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### A short-range alternative to LiDAR

This is borderline into a "shopping question" that aren't a great fit for the site. To that end I'm going to answer you in as generic a way as possible. Commonly available LIDARs can have ...
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### Merging multiple LIDARs real time

Certainly merging two laser scans into a single point cloud is doable. Here's an example tool and you can easily concatenate said point clouds too. However I'd like to suggest that you reconsider some ...
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### Reflective surface

Reducing reflection on an image is hard, really hard, because you only have the pixels, and they are most likely white. So changing the environment to get good images is the desired solution. Robotiq ...
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### Trouble aligning/calibrating camera with laser scanner

Within ros there is a lidar_camera_calibration package that should take care of this for you! Their github page has a detailed readme. If you aren't using ros, you can probably take a look at the core ...
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### 2D point cloud registration success probability

Matching point clouds can be very tricky. It is kind of a needle-in-a-haystack type of problem when you don't have an initial guess at the correspondence. As you found, if the point clouds are very ...
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### why custom generated pointcloud2 is displayed as line on rviz?

Comparing my code to the link sent by @Tully above, I could found the mistake. Here's the corrected code ...
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### Pipeline for dense reconstruction using pose estimation from orb-slam and stereo camera

Small errors and outliers in camera poses will make the reconstruction unprecise, hence you need some refinement. You have multiple options: Fuse the point clouds with an ICP-like algorithm. Use a ...
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### How to deal with inexact pointcloud matching?

You probably mean ICP, not IPC. The most typical way is using plane features. Plane information could be extracted by voxelisation and NDT. Plane-to-point or plane-to-plane is enough for the ...
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### PointCloud2 parse to xyz array in ROS2

Look in the sensor_msgs_py package. It contains support functions for working with some of the more complex sensor messages, including point clouds. For your ...
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### Unintentional point cloud duplication during depth image conversion

I agree with r-bryan that you're likely missinterpreting some of the metadata. It could be the frame width or alternatively the stride width or something else in the depth image. There's a good ...
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### Unintentional point cloud duplication during depth image conversion

At first I thought there was some sort of systematic raw format or resolution error, sort of like ROS + kinect depth data duplication . Then I noticed that each corridor appears in a different ...
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### What is the definition of the contents of PointCloud2?

The height for the Velodyne-HDL64e LiDAR is one because it is an unorganized datasets. This is because pointclouds won't have the same amount of points in dynamic scenarios (if nothing is "seen&...
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### How to convert PointCloud2 message to a grid?

What you're looking for is a coordinate transformation. You could make a node that takes in a pointcloud2 message and outputs a message with the data in a cylindrical format. This website has a ...
1 vote

### Calculating the distance of a point from point cloud data

The XYZ readings from the camera are in the reference frame of the camera. @FooBar is correct about the X/Y values: they are planar about the center of the camera, just like the OpenGL viewing window. ...
1 vote

### how to find space in point cloud larger than given l*b

Why don't you try to look it au contraire? Given you know the robot's "radius" (a contact free sphere actually with your desired r value) you can enlarge obstacles you find, although this would ...
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### 3D mapping using only a 2D Lidar

As the previous answers stated: You need an additional source of information to reconstruct the orientation of the scanner. Even if only roughly. Do a Google search for "Zebedee scanner". The ...
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### 3D mapping using only a 2D Lidar

If it was fixed: - You can place it vertically and define a rotating mechanism so it spins on itself and the 2D beam eventually maps the 3D surroundings. If it is hand-held: - You will have to ...
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### Methods for odometry/IMU/Gyro free lidar pointcloud registration for pose estimation

I'm not sure what sort of ICP did you used but a voxel based plane-to-point ICP is robust and works well even in an unstructured environment. This or his previous paper describes the method. http://...
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### Iterative Closest Point for 2-D LIDAR Data

This is what worked for me (to auto-align sparse scans, which can also be useful in SLAM when it gets lost): Run a corner detector for each scan (convert the LIDAR output into a single path and run a ...
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### Forward monocular stereo vision (Structure from Motion)

It turns out this can easily be done with OpenCV - just find image features (FAST etc.) in first image, track them to the second image (get a set of corresponding features between two images) and then ...
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### Calibrating a laser scanner to a line camera

I converted my comments to an actual answer: If I understand your setup correctly, you're saying you have a line scan camera mounted to the top of the rotating head of a laser scanner, and all you're ...
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