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Version française

Menu: File / Registration / Point to Point

This tool will move a given point cloud to match

Version française

The Point-to-Point Registration tool aligns a point cloud with a reference point cloud

. By

by selecting

at least 3

corresponding points

within both files

in both datasets. Using a minimum of three corresponding points, the algorithm calculates

and processes

the necessary translation and rotation

needed

to

move the second file accordingly

correctly reposition the moving point cloud. The adjustment is

made

performed using the least squares method to minimize errors.

How to Use the Point-to-Point Registration Tool

1. Selecting Files

To begin,

  • Choose the reference file and the file to be moved

must be chosen with

  • from the drop-down list.

Next, you must click on the “Show” button to view both clouds individually: the reference file

  • Click “Show” to display both point clouds:

    • The reference cloud appears in the main window

and the file

    • .

    • The cloud to be moved is shown in a secondary window.

To begin the registration, corresponding points must be added with the “+”  click on “Pick reference point” to select

2. Picking Corresponding Points

  • Click “+” to add a new control point.

  • Select “Pick reference point” and click on a point in the main window. The XYZ coordinates

for the reference point will then appear

  • will be recorded in the table.

Retrieve the same area

  • Find the corresponding location in the secondary window,

click on “Pick “to move” point” and select a point corresponding to the same element. Once this is done, XYZ coordinates will be added for the “to move” point. Both point clouds need to overlap at least in part and at least 3 corresponding are needed for this registration method to work, but it is recommended to have at least 7 points to better judge the residual error and uncheck unwanted points where the residual is too high. It’s also preferable to vary the position of control points: try to have corresponding points in different sectors and elevations. The “X” button will suppress concordant points while unchecking them only discards them from calculations.

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Once the control points are acceptable, the “Validate” button will analyse the transformation and show the difference between the XYZ points, the standard deviation of the transformation and the values of the translation and rotation calculated. The results can then be analysed and points may be re-picked, deleted or new points may be added for better results. Once the results are satisfying, click on “Apply” for the transformation between both scans which allows the user to view what the results would look like by showing both scans together in the main window. The “Back” button will remove any changes applied and will undo the transformation, while the “Reindex and reopen” button regenerates the index of the point cloud, making the change permanent. Note that if you “Apply” the transformation and quit VisionLidar, the index will automatically be recreated – this operation is also completed following the opening of a project. The “Report” button will save the results of the transformation in .TXT format giving a report of all points picked with the standard deviation and transformation values applied.

The registration could be made with an external file or reference file.  To do so, you must check the option “External file” and select the file to be used.  In this case the file to “move” is moved according to the external file.

When an external file is used, clicking on the “Reindex and reopen” button will create a new LAS file with the points at the new coordinates.

  • then select “Pick to move point” to assign a matching point. The coordinates for this point will also be added to the table.

  • At least three corresponding points are required for the registration to function, but seven or more points are recommended to improve accuracy and assess residual errors.

  • Best practices:

    • Distribute control points across different sectors and elevations.

    • Identify and remove points with high residual errors by unchecking them in the table.

    • Use the “X” button to delete selected control points.

3. Validating and Applying the Transformation

  • Click “Validate” to analyze the transformation. The software will display:

    • Differences between corresponding XYZ points.

    • Standard deviation of the transformation.

    • Calculated translation and rotation values.

  • If necessary, adjust the selection by adding, removing, or refining control points.

  • Once the results are satisfactory, click “Apply” to preview the transformed point cloud in the main window.

4. Finalizing the Registration

  • Click “Back” to undo the transformation.

  • Click “Reindex and Reopen” to permanently apply the transformation and regenerate the point cloud index.

  • If you apply the transformation and close VisionLidar, the index will be automatically updated when reopening the project.

5. Exporting a Registration Report

  • Click “Report” to generate a .TXT report containing:

    • All selected control points.

    • The standard deviation of the transformation.

    • Applied translation and rotation values.

Using an External Reference File for Registration

  • Enable the “External File” option to use an external reference file instead of a previously loaded point cloud.

  • Select the external file, and the “to move” point cloud will be aligned accordingly.

  • When using an external reference file, clicking “Reindex and Reopen” will generate a new LAS file with the updated coordinates.

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