User Coordinate System; Understanding Scan Coordinates And Coordinate Systems - Leica ScanStation P30 Basic Training Manual

5 User Coordinate System

Understanding Scan Coordinates and Coordinate Systems

There are certain situations in 3D laser scanning where a full Registration for the purposes of
geo-referencing is not necessary based on the deliverables required. For the registration
process, a minimum of 3 points (within three axes - X,Y,Z) in the project must be known and
scanned for the transformation (rotation and translation of the ScanWorlds) to work. Typically
more than 3 points are used to allow for redundancy and reduction of errors. However,
depending on the final deliverables, a full registration process may not be necessary.
Examples of deliverables that might not require full Registration (for Geo-referencing) are:
• A 2D planimetric map (no topography or elevations)
• A 3D topographic map of a relatively small area (e.g. 200m X 200m)
For these situations, Cyclone has the capability of setting the project coordinate system using a
variety of methods described further in this document. These methods are listed below:
Translation of existing coordinate system to user-defined reference point.
•
• Translation to new reference point, orientation measured by user entered azimuth
• Up direction set by vertical pair(s) of points, orientation by azimuth
• Up direction set by known elevation points (benchmarks), orientation by azimuth
In each of these cases, the XYZ coordinate basis of the scanner is transformed into "real world"
Cartesian coordinates that are either known (control) or assumed (defined by user). For each
case, the minimum number of constraints is used to determine the new coordinate system, and
there is little or no information to detect blunders. The user must be careful to use the best
practices as described in this document to avoid misuse of these features.
For 3D laser scanning surveys that require the data be geo-referenced to an existing
•
coordinate system, Leica Geosystems highly recommends that the standard Registration
process be used with a redundant amount of control points.
Furthermore, even a geo-referenced dataset might require the set-up of a more local site-
coordinate system. This could be aligned to specific buildings/ objects or local height markers. It
can be for ease of modeling or to fulfill client specific requirements.
Organization/Visualization point clouds
Module 4.0 – Point cloud Modifying 19 - 34