Point Pairs Registration

The point-to-point registration tool can be used for data correction between point clouds, images, and model data. Click the "Point-to-Point Registration (R2)" button to enter the registration tool. The main view is split into three sections: the top-left view contains reference data, the top-right view contains data to be registered, and the bottom view shows a preview of the registration results. Simultaneously, a manual point selection toolbar appears in the upper-right section of the software.

Point Pair Registration by Reference Files

1. Select or fit spheres (for point cloud data) in two windows to obtain at least three pairs of corresponding points. These corresponding points are used to calculate the coordinate transformation matrix between the two datasets for coordinate correction. By selecting point pairs, the user can view the residuals between the datasets in the corresponding point pairs list.

   

2. (Optional) Users can click Open Data to load known corresponding points from external sources, thus skipping steps 4, 5, and 6.

3. Click Select Corresponding Points or Select Target Sphere to select a point as the corresponding point in both the reference and registration windows.
4. After selecting a pair of corresponding points, click the Add Row button to add an empty row.
5. Repeat steps 3 and 4 to select at least three pairs of corresponding points.
6. (Optional) If a certain pair of corresponding points is not needed for coordinate transformation, there are two ways to achieve this: (1) Uncheck the row in the list; (2) Click Delete Corresponding Points to remove point pairs with large residuals.
7. (Optional) If the residual of a pair of corresponding points is large or if you want to correct the coordinates of the point pair, there are two ways to achieve this: (1) Select the corresponding point pair in the list and reselect the point in either the reference or registration window; (2) Double-click the coordinate value you want to modify and edit it directly.
8. (Optional) To view a particular pair of corresponding points, double-click the pair in the list to center it in the window.
9. (Optional) Click Save Data to save the selected corresponding points.

Registration Steps Using Control Points as Reference

1. Click Load Control Points. Control point information is displayed in both the reference and registration windows. Users can toggle the display of control points in the registration window. Select the corresponding control points in the table and choose corresponding points in the registration window. These corresponding points are used to calculate the coordinate transformation matrix between the two datasets for coordinate correction. By selecting point pairs, users can view the residuals between the datasets in the corresponding point pairs list.

   

The other operations are the same as the point pairs registration steps using reference files.

If the "Use GCP Targets" option is checked, target recognition functionality is enabled.

Manually Select Target: Click the target center position in the point cloud within the Alignment window. Target recognition is performed based on point cloud intensity information. For failed recognitions, adjust the correlation coefficient and reselect the target center. At least 5 target points must be selected for automatic target alignment. Avoid placing multiple targets in a straight line or forming equilateral triangles.

Auto-Align Selected Targets: After manually selecting temporary targets, click this function to automatically identify matching relationships between targets and imported control points, renaming selected targets with control point names.

Manually Adjust Target Position: For already identified targets, click this button, select the target to modify in the table, and fine-tune its position in the pop-up interface.

Auto-Identify Targets: Using aligned targets and control point information, automatically identify and precisely locate target centers nearest to remaining control points based on point cloud intensity. Automatically calculate other target center positions. ### Toolbar ###

In the toolbar, the buttons from left to right are: Load Pair Points, Save Data, Add Point, Delete Points, Pick Points, Pick Registration Sphere.

Load Pair Points: Import an existing corresponding points list file from external sources. For details on the format of the corresponding points list, refer to the appendix Homologous Points File Format.

Save Data: Save the selected corresponding points list as a txt file.

Add Point: After selecting a pair of corresponding points, click this button to add a new row in the table window.

Delete Point: To delete a row of corresponding points, select the row and click this button.

Pick Points: Select the corresponding points in the reference and registration windows.

Pick Registration Sphere: If using target spheres for matching in the point cloud, this tool can be used to select and automatically fit the target sphere. The coordinates of the corresponding point will be the center of the sphere.

In the lower toolbar, the buttons from left to right are Point Size, Adjust Scale, Predict.

Point Size: The size of the selected points in the window.

Adjust Scale (default is "unchecked"): If the scales between the datasets are different, this option should be checked. If unchecked, the point clouds are considered to undergo a rigid transformation, and the calculated rotation matrix will not include a scaling factor. If checked, the rotation matrix will include a scaling factor.

Predict (default is "unchecked"): Check this box and after selecting more than three pairs of corresponding points, the corresponding point in the reference window can be predicted after selecting the corresponding point in the registration window.