Tip 30: Using Sphere Targets and Laser Scan Data
This tip is a follow-on to the Tip 29 blog posting and video. In Tip 29 we showed how the new Sphere Target can be used in PhotoModeler to get precise photogrammetric marking and measurement.
Some laser scanners, such as (but limited to) the Faro Focus 3D, can also use sphere targets for scan alignment. We take advantage of that to align a laser scan to a photogrammetric project to high accuracy.
Sphere targets are placed in the scene and both a laser scan and a set of photographs are taken. The laser scanner software outputs the centers of the spheres, which PhotoModeler then imports and are matched to the marked sphere targets in the photos. This places the laser scan data and the photogrammetry project in the same coordinate system (same scale, translation and rotation). The laser scan point cloud can then be imported into PhotoModeler. It will be aligned with the photos and the photogrammetric data.
There are a number of useful tasks you can do when your laser scan and photogrammetric project are in the same coordinate system. In the video, we demonstrate one such task – the high-accuracy photo-texturing of the laser point cloud.