Abstract
Abstract. The advancement of permanently measuring laser scanners has opened up a wide range of new applications, but also led to the need for more advanced approaches on error quantification and correction. Time-dependent and systematic error influences may only become visible in data of quasi-permanent measurements. During a scan experiment in February/March 2020 point clouds were acquired every thirty minutes with a Riegl VZ-2000 laser scanner, and various other sensors (inclination sensors, weather station and GNSS sensors) were used to survey the environment of the laser scanner and the study site. Using this measurement configuration, our aim is to identify apparent displacements in multi-temporal scans due to systematic error influences and to investigate data quality for assessment of geomorphic changes in coastal regions. We analyse scan data collected around two storm events around 09/02/2020 (Ciara) and around 22/02/2020 (Yulia) and derive the impact of heavy storms on the point cloud data through comparison with the collected auxiliary data. To investigate the systematic residuals on data acquired by permanent laser scanning, we extracted several stable flat surfaces from the point cloud data. From a plane fitted through the respective surfaces of each scan, we estimated the mean displacement of each plane with the respective root mean square errors. Inclination sensors, internal and external, recorded pitch and roll values during each scan. We derived a mean inclination per scan (in pitch and roll) and the standard deviation from the mean as a measure of the stability of the laser scanner during each scan. Evaluation of the data recorded by a weather station together with knowledge of the movement behaviour, allows to derive possible causes of displacements and/or noise and correction models. The results are compared to independent measurements from GNSS sensors for validation. For wind speeds of 10 m/s and higher, movements of the scanner considerably increase the noise level in the point cloud data.
Highlights
Terrestrial laser scanning (TLS) is an established measurement technique that has evolved continuously over the last two decades
Various research groups use permanently installed laser scanners to address a wide range of research topics, including i2MON (Schroder and Klonowski, 2019) and CoastScan (Vos et al, 2017), (Kuschnerus et al, 2021)
The results are presented in four parts: First, we evaluate the inclination sensors on the scanner and correlate the measured values with the weather data
Summary
Terrestrial laser scanning (TLS) is an established measurement technique that has evolved continuously over the last two decades. Increasing operating ranges, the ability of automatic processing on the scanner itself or new algorithms for georeferencing are just a few examples of the improving functionality of sensor techniques. Various research groups use permanently installed laser scanners to address a wide range of research topics, including i2MON (Schroder and Klonowski, 2019) and CoastScan (Vos et al, 2017), (Kuschnerus et al, 2021). The quality of results depends on many factors comprising the measuring system (Schroder and Nowacki, 2021). The appearance of permanently measuring sensors has made influences visible that were previously not apparent in campaign-based measurements at individual selected measurement times. Time-dependent, systematic error influences appear in time-series of quasi-permanent measurements (Schroder and Nowacki, 2021), (Friedli et al, 2019), (Anders et al, 2019)
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