After successful data acquisition, the data evaluation of the point cloud can be carried out with the CADdy workflow in the “CADdy V for BricsCAD” plug-in.
Point clouds recorded with the lidar sensor of the iPhone can be exported with known file formats. These formats (such as PLY, LAS, OBJ) are also known to BricsCAD and the CADdy-V plug-in and can be read in with just a few clicks.
The BricsCAD-V21 on-board function “Insert -> Attach point cloud” is used to visualize the data, for example in LAS format. The point cloud is embedded in a DWG drawing with its original coordinates. It will look like that:
(Sample data recorded with the iPhone 12pro on the Schatzbogen office terrace, Munich)
However, this data has not yet been georeferenced and this is where transformation functionality from the CADdy-V plug-in comes into play.
In the example you can see a good 3 control points that can be quickly recorded with centimeter accuracy using GPS. In order to determine the local coordinates that match the control points, the points can be digitized in the DWG, for this purpose BricsCAD offers a convenient 3D snap at individual point cloud points. The 3D measurement points are then saved directly in the CADdy coordinate management.
(Digitize in the point cloud / 3D point snap with blue cross marker)
(completely recorded local control point data)
The world coordinates of the 3 control points (with identical point numbers) are kept in an ASCII coordinate file, such as in the CADdy-KOR format:
(World control point data in KOR format)
The CADdy-V transformation library also offers a 7-parameter Helmert transformation which, after our preparations, now generates world coordinates from the local point cloud with just a few clicks.
(User interface for 7-parameter transformation)
After calculating the Helmert transformation parameters, the transformation can be applied directly to the point cloud file originally created by the iPhone (button “Transform external file”) and this can be re-attached to a DWG, but this time correctly georeferenced.
(georeferenced point cloud in UTM32 coordinates)
