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J. Paffenholz, C. Harmening:
"3D point cloud based spatio-temporal monitoring of artificial and natural objects";
in: "Proceedings of FIG Working Week 2020", FIG (ed.); issued by: FIG; FIG (International Federation of Surveyors), 2020, (invited), 13 pages.

This paper aims to provide an overview of the field of 3D point cloud based spatio-temporal
monitoring. The focus is on spatio-temporal monitoring of artificial and natural objects with
the aid of 3D point clouds acquired by means of multi-sensor-systems (MSS) with a laser
scanner as a main object capturing sensor.
First, we discuss the technical aspects of the MSS for 3D point cloud acquisition with respect
to monitoring applications. In particular, the challenges and chances of the surface-based
technique will be outlined. Second, we highlight some results of self-conducted experiments:
We focus on the evaluation of an object´s abstraction for epochal comparison by means of area-based
and shape-based approaches as well as on loading tests of a historic masonry arch bridge.
The first showcase deals with the abstraction of natural objects by means of B-spline surfaces.
For this purpose, 3D point clouds of plant leaves are investigated with the aim to obtain
measures of interest like overall sizes and area. For the second showcase, we present results of
the load-induced arch displacements on a bridge by means of 3D point clouds acquired by
terrestrial laser scanning. In detail, we discuss different approaches for the deformation analysis
based on the captured 3D point clouds, i.e., the multiscale model-to-model cloud comparison
(M3C2) algorithm or a parametric procedure by means of B-spline approximation. We conclude
our paper with some perspectives on the upcoming work plan of the IAG working group 4.1.3
in close cooperation with the FIG commission 6 to make significant contributions to the 3D
point cloud based spatio-temporal monitoring of artificial and natural objects. The next steps
will be the abstraction of natural soil erosion scenes to quantify volumes. Our take home for the
reader is: we are open for your contributions and your participation in the working group and
commission work. The authors are happy to hear from you!

Bridge surveying; Deformation measurement; Engineering survey; Laser