Fine Registration & Report

The fine registration page provides the final view of the registered data, including statistics about the fit as well as the final matrices.

The fine registration processing tries to find the best global fit of the data. It does this by the following:

• at each scan position, finding scans that are up to the maximum scan-to-scan distance away and within the minimum acceptable overlap (default 2%)
• adjusting this neighbourhood of scans to minimise errors.

The fine registration page has two parts to enable checking the result:

• the 3D view of the data on the left
• the scans and statistics on the right

The 3D view can be read about in more detail here. Clicking on the scan names turns them on or off in the 3D view.

Some summary statistics are shown on the right, along with links to download the final registered matrices and the full registration report.

The final point-to-point error is generally larger than the point-to-plane error due to the subsampling of the original data. Therfore the point-to-plane error is usually a better measure of the accuracy of the full resolution data.

Matrices

The matrices button allows you to download a csv file of the absolute transformation matrices in 4×4 format in row order, for each scan. These can be used as required in third party software to transform the original scans to their registered positions.

A 4×4 transformation matrix is divided into rotations (in blue), translations (in green) and the scale (in red).

The csv is ordered as follows per line:

scan_name, a11, a12, a13, a14, a21, a22, a23, a24, a31, a32, a33, a34, a41, a42, a43, a44

 

Registration Report

The registration report contains a text file report of the final accuracy of the registration between all of the scans assessed.

The elements contained within the report are outlined below.

Term Definitions

Maximum scan-to-scan distance

The maximum distance between scans to form clusters in the global ICP to adjust scans locally; chosen by the user in settings

Maximum point search distance

The maximum distance to search from the target to the reference point cloud for a match; chosen by the user in settings

Child Scan

The subject scan

Parent Scan

The fixed reference scan

Mean Point-to-Plane Error

The average (mean) rms error calculated from each point in the child to the best fit plane in the parent, limited by the search threshold. This value can be more accurate for the underlying data as it is affected less by subsampling than point-to-point.

Mean Point-to-Point Error

The average (mean) rms error calculated from each point in the child to the closest point in the parent, limited by the search threshold. This value will be less accurate for the underlying data as it is affected more by subsampling than point-to-plane.

Scan-to-Scan distance

The distance between scan positions

Overlap fraction

The fraction of the child that is matched in the parent, based on the search threshold

RMS point-to-plane distance

The root mean square error calculated from each point in the child to the best fit plane in the parent, limited by the search threshold. This value can be more accurate for the underlying data as it is affected less by subsampling than point-to-point.

RMS point-to-point distance

The root mean square error calculated from each point in the child to the closest point in the parent, limited by the search threshold. This value will be less accurate for the underlying data as it is affected more by subsampling than point-to-plane.

Number of Overlapping Points

The number of points in the child that overlap with the parent with overlap defined by the maximum search distance.