Traditionally, this alignment has depended on artificial targets that are placed throughout the scan field in areas of overlap. The capability to align point clouds using natural features has existed for years. But, targets have remained the dominant means of registering scans because of inefficiency in processing software. You pay for time saved in the field with time spent in the office.
For example, using traditional software to align 130 scans using targetless registration can take up to 28 hours. This would be fine, but conventional software also requires manual processes (setting scan parameters, cross-check data, etc.) throughout the procedure. Turning that 28 hours into more than three days of constant work.