This is the way to connect scanns together and to place them in the proper place in space.
If You are scanning the house You have to make a few scanns.
They are in so called SCS - Scann Coordinate System where the origin is the origin of the scanner and the Z axe is an vertical axe of the scanner.
You can connect scans together to see whole the buiding and then they are in LCS - Local Coordintate System.
Finally there is an GCS - Global Coordinate system where scans are together and the building is in the proper place on the city map.
Procedure leading to GCS is an statistic calculation where the common points on scans are needed.
ASCAN gives You functionallity to measure common points and to solve this task.