1. Introduction

LAS to LAS auto registration is a tool available in LP360 Land starting from v2024.2. The module can be found on the Tools ribbon section. LAS to LAS registration requires "LP360 Land Standard" license or the "LP360 Land Standard" addon.

Auto registration is a tool performing fine alignment, in other words it performs an automatic alignment once 2 LAS are close to eachother or it refines their alignment.

If you are looking for other types of registration, please check the article on LAS to Control registration or LAS to LAS Manual registration.

2. How to use LAS to LAS Auto Registration

Before using LAS to LAS automatic registration, ensure the reference and registered point clouds are initially well-aligned, with overlapping regular surfaces.
LAS to LAS automatic registration can only be performed with point clouds with overlap surfaces areas.

2.1. Prerequisites

The tool is used to refine the alignment between two models that are relatively align with each other. This means that the tools is not able to directly align automatically two models that are apart, for example a SLAM and a RTK/PPK. In these cases, a pre-requisite will be required:

Cases:

a) SLAM to SLAM: Use LAS to LAS manual registration before performing automatic registration, at least to have both point clouds relatively aligned.

b) SLAM to RTK/PPK: Use LAS to LAS manual registration before.
c) RTK/PPK to RTK/PPK: Directly use automatic registration.
d) SLAM to drone mapping: Use LAS to LAS manual registration before.
e) RTK/PPK to drone mapping: Directly use automatic registration.

2.2. How to use it

1. Open LAS to LAS Auto Registration tool.
2. Select the "Reference LAS Layer"
3. Select the "Registered LAS Layer"
4. Press "Solve", the tool will calculate the values to be applied to the registration
5. Review the registration values.
Tip: review the fitness score, it means how well 2 points clouds align with each other. The "After" value should be smaller than the "Before" value.
6. Press "Apply Corrections"

7. A new registered point cloud will be created in the table of content

3. Advance settings

Search Radius: To define 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

Max distance: max distance to consider a correspondence

Max angle: max angle between normals to consider a correspondence

Distance Type:

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

4. Good practices

- When registering SLAM data to georeferenced data, always perform LAS to LAS manual registration before.
- It is important to have common overlap surfaces between point clouds.
- Use the most confidence point cloud as reference.
- Review the "Key points" and "Used Key points" after pressing "Solve", in the previous screenshot you can see them in "white" and "red" colour. They should be consistent in all the overlap area. These points should be picked in flat surfaces and not in irregular features like trees.