Permanent terrestrial laser scanning for environmental monitoring

Many topographic scenes demonstrate complex dynamic behavior that is difficult to map and understand. A terrestrial laser scanner fixed on a permanent position can be used to monitor such scenes in an automated way with centimeter to decimeter quality at ranges of up to several kilometers. Laser scanners are active sensors, and can continue operation during night. Their independence from surface texture properties ensures in principle that they provide stable range measurements for varying surface conditions.

Recent years have seen an increase in the employment of such systems for different applications in environmental geosciences, including forestry, glaciology and geomorphology. This employment resulted in a new type of 4D topographic data sets (3D point clouds + time) with a significant temporal dimension, as such systems can acquire thousands of consecutive epochs.

However, extracting information from these 4D data sets turns out to be challenging, first, because of insufficient knowledge on error budget and correlations, and second, because of lack of algorithms, benchmarks, and best-practice workflows.

The presentation will showcase recently active systems that monitored a forest, a glacier, an active rockfall site and a sandy beach respectively. Data from these systems will be used to illustrate different systematic challenges that include instabilities of the sensor system, meteorological and atmospheric influence on the data product and the maybe surprising need for alignment of point clouds from different epochs.

In addition, different ways to extract information from these 4D data sets will be discussed, in connection with particular applications. While bi-temporal change detection is often a starting point for exploring 4D data, several methods are being developed that truly exploit the extensive time dimension, including tracking, trend analysis, time series clustering and spatio-temporal region growing.

Lessons learned from experiences with these systems in different domains lead to several recommendations for future employment considering field of view design, auxiliary sensors (e.g. IMU, camera, weather station) and the possible deployment of low-cost alternatives, thereby providing a view on the near future of permanent laser scanning.

Reference

Lindenbergh, R., Anders, K., Campos, M., Czerwonka-Schröder, D., Höfle, B., Kuschnerus, M., Puttonen, E., Prinz, R., Rutzinger, M., Voordendag, A & Vos, S. (2025). Permanent terrestrial laser scanning for near-continuous environmental observations: Systems, methods, challenges and applications. ISPRS Open Journal of Photogrammetry and Remote Sensing, 17, 100094. DOI: 10.1016/j.ophoto.2025.100094