4D objects-by-change

4D objects-by-change: Spatiotemporal segmentation of geomorphic surface change from LiDAR time series

Anders, K.P. (University of Heidelberg)
Winiwarter, Lukas (University of Heidelberg)
Lindenbergh, R.C. (TU Delft Optical and Laser Remote Sensing)
Williams, Jack G. (University of Heidelberg)
Vos, S.E. (TU Delft Coastal Engineering)
Höfle, Bernhard (University of Heidelberg)

2020

Time series of topographic data are becoming increasingly widespread for monitoring geomorphic activity. Dense 3D time series are now obtained by near-continuous terrestrial laser scanning (TLS) installations, which acquire data at high frequency (e.g. hourly) and over long periods. Such datasets contain valuable information on topographic evolution over varying spatial and temporal scales. Current analyses however are mostly conducted based on pairwise surface or object-based change, which typically require the selection of thresholds and intervals to identify the processes involved and fail to account for the full history of change. Detected change may therefore be difficult to attribute to one or more underlying geomorphic processes causing the surface alteration. We present an automatic method for 4D change analysis that includes the temporal domain by using the history of surface change to extract the period and spatial extent of changes. A 3D space-time array of surface change values is derived from an hourly TLS time series acquired at a sandy beach over five months (2967 point clouds). Change point detection is performed in the time series at individual locations and used to identify change processes, such as the appearance and disappearance of an accumulation form. These provide the seed to spatially segment ‘4D objects-by-change’ using a metric of time series similarity in a region growing approach. Results are compared to pairwise surface change for three selected cases of anthropogenic and natural processes on the beach. The obtained information reflects the evolution of a change process and its spatial extent over the change period, thereby improving upon the results of pairwise analysis. The method allows the detection and spatiotemporal delineation of even subtle changes induced by sand transport on the surface. 4D objects-by-change can therefore provide new insights on spatiotemporal characteristics of geomorphic activity, particularly in settings of continuous surfaces with dynamic morphologies.

Beach monitoring
High-frequency observation
Spatiotemporal analysis
Temporal domain
Terrestrial laser scanning

http://resolver.tudelft.nl/uuid:a909c681-50cd-4bb1-8fa7-5770b4889afa

https://doi.org/10.1016/j.isprsjprs.2019.11.025

2021-12-09

0924-2716

ISPRS Journal of Photogrammetry and Remote Sensing, 159, 352-363

Accepted Author Manuscript

Institutional Repository

journal article

© 2020 K.P. Anders, Lukas Winiwarter, R.C. Lindenbergh, Jack G. Williams, S.E. Vos, Bernhard Höfle