Requires an LP360 Land Standard, an LP360 Geospatial Advanced, or a BIT add-on for LP360 Drone license.

Introduction

LAS to LAS Auto Registration on the Tool Tab and TVGO Tab of the ribbon is used to perform fine alignment. In other words, it performs an automatic alignment once two LAS Layers are close to each other or it refines their alignment. It is typically run after having performed a gross adjustment using either the LAS to Control Manual Registration or LAS to LAS Manual Registration tools.

Figure 1: LAS to LAS Auto Registration in the Tools Tab

Figure 2: LAS to LAS Auto Registration dialog

Input Files

Registered LAS Layer: The LAS Layer to be registered to the Reference LAS Layer. 

Reference LAS Layer: The LAS Layer to be used as the reference layer. Points in this layer are not written to the output.

Parameters

Registered / Reference Morphology

Search Radius: Defines the area around each point that will be used to determine the morphology of the terrain at this point

Min Neighbors: Minimum number of points in the neighborhood of a point to be considered

Max Thickness: Maximum thickness (obtained after determining the morphology) for a point to be considered

Correspondences

Distance Type:

• • Point2Point: Euclidean distance based correspondence estimation.
  • Point2PointWithAngleNormal: Euclidean distance based correspondence estimation taking into account point normals.
  • Point2Line: Point to Line based correspondence estimation.

Max distance: max distance to consider a correspondence

Max angle: max angle between normals to consider a correspondence

Results

Corrections: The origin, translation, and rotation values of the derived rigid correction. Populated by executing Solve.

Fitness Score: describes how well the two input point clouds align. The "After" value should be smaller than the "Before" value to see any improvement in the alignment. Populated by executing Solve.

Commands

Help to open this help page.

Reset to restore the Parameters to default values.

View / Close Points will display the LAS to be registered and the "Reference LAS Layer" in separate Immersive Viewers. Close will close those viewers.

Solve will calculate the values to be applied to register the "Registered LAS Layer" to the "Reference LAS Layer" and display the Fitness Score. The input point clouds will be shown in separate Immersive Viewers with the auto selected points used for the registration highlighted in red and white. They should be consistent in all the overlap area. These points should be picked in flat surfaces and not in irregular features like trees.

Apply Corrections to create the output layer which will contain the corrected points from "Registered LAS Layer" and have the naming convention, NameofRegisteredLASLayer_Auto_Registered_YYMMDD_hhmmss, where the date and timestamp in the name correspond to when the Apply Corrections was executed.

Cancel to close the tool without applying corrections.

Prerequisites

Before using LAS to LAS Auto Registration, ensure the reference and registered point clouds are initially well-aligned, with overlapping regular surfaces. Automatic registration may only be performed between point clouds with overlapping surfaces areas where the alignment between two models is relatively aligned. The tool is not able to automatically align two models that are far apart, for example a SLAM dataset in a local reference frame and an RTK or PPK dataset in a known coordinate reference system (CRS). In these cases, a pre-requisite operation is required.

Examples

a) SLAM to SLAM: Use LAS to LAS Manual Registration  to have both point clouds relatively aligned before performing the automatic registration.

b) SLAM to RTK/PPK: Use LAS to LAS Manual Registration before performing the automatic registration.
c) RTK/PPK to RTK/PPK: Directly use the automatic registration if the point clouds relatively aligned.
d) SLAM to drone or aerial acquired point cloud: Use LAS to LAS Manual Registration before performing the automatic registration.
e) RTK/PPK to drone or aerial acquired point cloud: Directly use the automatic registration if the point clouds relatively aligned.

How to use LAS to LAS Auto Registration

1. Open LAS to LAS Auto Registration on the Tool Tab or TVGO Tab of the ribbon.
2. Select the "Reference LAS Layer".
3. Select the "Registered LAS Layer".
4. Press "Solve".
5. Review the computed registration values and review the fitness score.
6. Press "Apply Corrections".

Figure 3: LAS to LAS Auto Registration dialog with corresponding steps numbered.

7. A new registered point cloud will be created and added to the Table of Contents (TOC).

Figure 4: LAS to LAS Auto Registration Results

Good Practices

• When registering SLAM data to georeferenced data, always perform LAS to LAS Manual Registration first.
• It is important to have common overlap surfaces between point clouds.
• Use the most confident point cloud as reference.
• Review the "Key points" and "Used Key points" after pressing "Solve". In Figure 3, you can see them in "white" and "red" color. They should be consistent in all the overlap area. These points should be picked in flat surfaces and not in irregular features like trees.