Post-Processing with Control Points

When measured control points are used in a Dataset, post-processing automatically generates a registered Point cloud. Control points help the automatic alignment of the dataset within Navvis IVION. To use measured control points, add the path to the control point poses file to the SiteMaker project.

Note: Control points were previously called SLAM Anchors. You might occasionally encounter that name in file names.

To post-process with measured control points, you need to provide a Control Point Poses File that contains the coordinates (control point poses) of each control point, measured relative to a common reference frame. This reference frame is a local coordinate system selected so that its origin is close to the scanned Site.

The control point pose information is used during post-processing to undistort the device's trajectory and to extract information required later for automatic alignment of the processed datasets.

Note: For automatic dataset alignment, all control point poses of the site must be measured in the same reference frame.

To use surveyed control points in post-processing, add the path to the control point poses file to the SiteMaker project. To process the dataset with surveyed control points, follow these steps:

1. Open NavVis SiteMaker.

2. Click the Settings tab.

3. From the Control Points section, select the Use control points for trajectory optimization and dataset registration checkbox.

4. From the Enter you control points (IDs + surveyed coordinates) either in .txt or .csv format field, click the "…" button and select the control point poses file from the file system.

   

   These settings can be changed both when creating a new project and in the settings.

5. Then, run the processing as usual.

Post-processing with surveyed control points generates an Error Log file. It shows how much error remains at each of the control points. Because there are three stages when post-processing with control points, you can also gauge the error between control points.