After taking over the raw data from the field, these are being downloaded from the central unit of the scanner, with the help of a USB stick. Following is the stage of processing the raw data. For this, we use GeoSLAM HUB for Desktop, which is the local processing version of the SLAM software (simultaneous location and mapping). The software is used to automatically record data captured by the GeoSLAM mobile scanner laser systems, to produce fully aligned 3D point clouds.
Tree validation is performed using a point layer with the data resulting from the segmentation process (diameter, height, position, etc.) for each tree in geographical coordinates, photospheres (360) taken during the scanning process which are positioned on the path (trajectory) of the scanner, raster image for each area scanned.
The species or group of species is validated by analyzing the graphic images of the dot cloud, having as main criterion the shape of the tree and the photospheres positioned on the scanner trajectory.
When all of the individual tree segments are identified, the remaining task is to recognize tree trunks and model their numerical dimensions on a simple and flexible basis, thereby giving the potential for the digital twinning process. To overcome the limitations of current techniques, VirtSilv algorithms are designed around the following principles:
The trunk shape of segments of sufficiently small height can be approximated very well by inclined cone trunks;
The vertical projection of the data obtained from segments of sufficiently small height can be approximated by a ring of points with relatively high density;
Generally, the successive segments in the vertical array are very well aligned, in the sense that the angle and bending of each segment, concerning that vertical changes are low.
Thus, the VirtSilv algorithm is focused on extracting chains of cone trunks as a numerical model for trunks. The average time of producing the 3D model of a tree digital twin is less than one minute.