Environmental Influences on the Stability of a Permanently Installed Laser Scanner

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.

Uncertainty assessment of a permanent long-range terrestrial laser scanning system for the quantification of snow dynamics on Hintereisferner (Austria)

“…Additionally, the rasterization of point clouds contributes to the uncertainty budget when working with a digital elevation model (DEM). Previous research assessed only selected uncertainty sources and at shorter distance ranges than the system at HEF (Soudarissanane, 2016;Friedli, 2020;Kuschnerus et al, 2021;Dong et al, 2020;Schaer et al, 2007). Here, we addressed the full spectrum of the main uncertainty sources of TLS point clouds and derived DEMs and at distances up to 4,500 m.…”

Keypoint-based deformation monitoring using a terrestrial laser scanner from a single station: Case study of a bridge pier

“…However, due to a cloudy sky, which hinders direct and uneven material heating, the deformations were expected to be far from the extreme values. Namely, the bridge bearings are designed for the maximum pier movement of ±550 mm at the highest elevation (Kuschnerus et al, 2021).…”

“…Hence, no atmospheric corrections were applied. To account for eventual instrument instability over time, which was reported in previous studies (Janßen et al, 2020;Kuschnerus et al, 2021), four dedicated BOTA8 scanning targets (Janßen et al, 2019) were placed on tripods around the scanner stations at distances of approximately 30 m. In the case of ZF5016, the targets were visible within each scan of the object of interest. Hence, all consecutive scans were registered to the local scanner coordinate system of the first scan (epoch 0).…”

“…To reach comparable deformations between ZF5016 and P50 data (Figure 3 and 4) it was necessary to account for instrument instabilities that can occur during long-term TLS observations (Janßen et al, 2020;Kuschnerus et al, 2021). In the case of the reference 5 th Joint International Symposium on Deformation Monitoring (JISDM), 20-22 June 2022, Valencia, Spain 2022, Editorial Universitat Politècnica de València dataset acquired by the ZF5016 scanner, this was done by accurate target-based registration (Section III).…”

Two-epoch TLS deformation analysis of a double curved wooden structure using approximating B-spline surfaces and fully-populated synthetic covariance matrices

“…It is also mentioned that these values are not used to correct the observations, since this is not of interest in this contribution. This resembles measurement set-ups used in permanent laser scanning for monitoring (Kuschnerus et al, 2021) that are recently receiving increased importance.…”