SA can search a point cloud and detect registration spheres within the cloud, and build the center points for those detected spheres.
Provide the command with the expected sphere diameter, acceptable RMS tolerance, and minimum number of points required, and the command will detect spherical data matching the proposed diameter from the scan data, fit spheres to them, and create their center points.
Create point from cloud sphere extraction now includes an option to perform a “Final Fit” option which implements ASTM E3125-17 fitting algorithms. The point cloud data is filtered so that only a central cone opening angle of 120° is used to compute the sphere and its center point.
Note that the input cloud must be associated with an instrument to establish the line of sight vector used for cloud segmentation as per this standard which then applies a conical outlier rejection strategy to further refine the fit results.
To Auto-Detect Sphere Centers from Raster Scan Data:
From the menu, select Construct>Points>From Cloud Points>Auto- Detect Sphere Centers.
The Sphere Extraction Settings dialog appears:
Sphere Diameter. The nominal or expected diameter of the registration spheres to detect from the cloud.
Search Tolerance. The maximum allowable deviation for a given point from the desired diameter in order to be considered.
Minimum Point Count. The minimum number of cloud points required to satisfy the tolerance to consider a sphere to be “found”.
Final Fit Parameters. When enabled this option employs the ASTM E3125-17 method for cloud point rejection using the instrument’s line of sight and the LOS Cone Angle specified.
Group to Contain Sphere Centers. The name for the resulting group to contain the sphere center points found.
Create Spheres in addition to points. When enabled, SA will create the spheres (at the desired diameter) in addition to the center points.
Select the desired options, then click OK.
After calculation, SA will display the Sphere Auto-Detection Results dialog. This contains the RMS error, maximum error, and point count for each detected sphere.
Click OK to accept the results, or Cancel to cancel.