Feasibility of Laser Bathymetry for Hydrographic Surveys on the Baltic Sea (original) (raw)
Related papers
Development of Bathymetric Techniques
2015
Preparation of modern nautical charts which are very essential to marine commerce safety, location of underwater works, coastal zone management, volume of underwater excavation, volume of water in lakes, fish and mineral industries are examples of application of underwater depth. Historically, the first hydrographic method used in water depth determination was the sounding line which has then been replaced by the acoustic sounding techniques that solved the problem of deep water depth measurement. Both techniques were shipboard instruments that have the limitation of efficiency and time consuming. This is why a vast area of world water bodies are still not covered for water depth determination. Recent techniques, all classified as remote sensing techniques including airborne LIDAR, airborne and satellite sensors that work with optical or radar waves are used to determine water depth especially for vast water areas such as seas and oceans. This paper is an attempt to review technique...
ACOUSTIC AND LASER BATHYMETRY SYSTEMS
This paper discusses acoustic and lasers based bathymetric systems in terms of their applicability in diverse circumstances. The advantages and disadvantages of each method are compared in terms of capabilities, cost and accuracy. None of these systems can provide full bottom coverage in all circumstances but could be supplementary to each other. Information has been presented in support of this conclusion. Acoustic bathymetry is suitable at deeper waters whereas laser bathymetry may be used in shallow clear coastal waters. A hybrid option has been suggested with the mix of these systems for higher survey efficiency and lesser costs. This paper is of interest to persons involved in ocean acoustics study and survey projects planners as well as to the developers of laser instruments for study ocean water and bottom properties and object detection such as wracks, boulders and other objects.
Airborne Lidar Bathymetry Applied to Coastal Hydrodynamic Processes
Coastal Engineering Proceedings, 2011
In this study, the possibility to get sedimentological (density, compaction) and hydrodynamical (suspended sediment concentration, turbulence) information from ALB surveys is demonstrated. ALB laser reflectance was found to be higher on the lee-side and on the crest of the ripple bedform than in the trough and on the stoss-side. Moreover, laser reflectance was also found to be higher on “active” subtidal dunes, located within the depth of action of the waves, than on deeper “passive” bedforms. Based on lab experiments conducted in a hydraulic flume under X-ray CT-Scanner, these observations were related to sediment compaction and suspended sediment.
Potential of space-borne LiDAR sensors for global bathymetry in coastal and inland waters
This work aimed to prospect future space-borne LiDAR sensor capacities for global bathymetry over inland and coastal waters. The sensor performances were assessed using a methodology based on waveform simulation. A global representative simulated waveform database is first built from the Wa-LiD (Water LiDAR) waveform simulator and from distributions of water parameters assumed to be representative at the global scale. A bathymetry detection and estimation process is thus applied to each waveform to determine the bathymetric measurement probabilities in coastal waters, shallow lakes, deep lakes and rivers for a range of water depths. Finally, with a sensitivity analysis of waveforms, the accuracy and some limiting factors of the bathymetry are identified for the dominant water parameters.
Analyzing near water surface penetration in laser bathymetry-A case study at the River Pielach
Recent developments in sensor technology yielded a major progress in airborne laser bathymetry for capturing shallow water bodies. Modern topo-bathymetric small foot print laser scanners do no longer use the primary near infrared (NIR) signal (λ=1064 nm) but only emit and receive the frequency doubled green signal (λ=532 nm). For calculating correct water depths accurate knowledge of the water surface (air-water-interface) is mandatory for obtaining accurate spot positions and water depths. Due to the ability of the green signal to penetrate water the first reflections do not exactly represent the water surface but, depending on environmental parameters like turbidity, a certain penetration into the water column can be observed. This raises the question if it is even feasible to determine correct water level heights from the green laser echoes only. In this article, therefore, the near water surface penetration properties of the green laser signal are analyzed based on a test flight of the River Pielach (Austria) carried out with Riegl's VQ-820-G (532 nm) and VQ-580 (1064 nm) scanners mounted on the same airborne platform. It is shown that within the study area the mean penetration into the water column is in the range of 10-25 cm compared to the NIR signal as reference. However, as the upper hull of the green water surface echoes coincides with the NIR signal with cm-precision, it is still possible to derive water surface models from the green laser echoes only via statistical analysis of aggregated neighboring echoes and robustly keep the underestimation of the water level below 6 cm. This especially holds for still and stationary flowing water bodies.
Airborne and mobile laser scanning in measurements of sea cliffs on the southern Baltic
DOI: 10.5593/SGEM2015/B12/S2.003 Conference: 15th International Multidisciplinary Scientific GeoConference SGEM 2015, www.sgem.org, SGEM2015 Conference Proceedings, ISBN 978-619-7105-32-2 / ISSN 1314-2704, June 18-24, 2015, Book1 Vol. 2, 17-24 pp, At Albena, Bulgaria Measurements of sea cliffs performed using periodic surveying based on laser scanning is currently one of the fastest and most accurate solutions. Supported with the technology of satellite measurements using GNSS (Global Navigation Satellite System) positioning and photographic measurements with the use of aerial vehicle, they enable an effective monitoring of the sea cliffs affected by the erosion. In case of the coast of southern Baltic, there are also the cliffs with a low angle of inclination and terraces; additionally there is a restriction concerning an access to the cliff from the shore side because of the narrow or non-existent lane of the beach. Hence there is a need for synergy of mobile measurements (Maritime Laser Scanning, MarLS) with airborne measurements
Remote Sensing
The development of bathymetric LiDAR technology has contributed significantly to both the quality and quantity of river bathymetry data. Although several bathymetric LiDAR sensors are available today, studies that evaluate the performance of the different bathymetric LiDAR sensors comparatively are still lacking. This study evaluates the performance of three bathymetric LiDAR sensors, CZMIL Supernova, Riegl VQ880-G, and Riegl VQ840-G, used with different acquisition approaches, in mapping Lærdal River bathymetry in Norway. The performance was evaluated based on comparing the sensors against a multibeam echosounder (MBES), a terrestrial laser scanner (TLS), and by an intercomparison between the individual sensors. The comparison was completed by comparing point clouds from the instruments and through the comparison of DEMs created from the point clouds. For the comparison against the MBES, the results show that the median residuals range between 3 to 13 cm, while against the TLS the ...
Bathymetric Properties of the Baltic Sea
Ocean Science Discussions, 2019
Marine science and engineering commonly require reliable information about seafloor depth (bathymetry), e.g. for studies of 10 ocean circulation, bottom habitats, fishing resources, sediment transport, geohazards and site selection for platforms and cables. Baltic Sea bathymetric properties are analysed here using the using the newly released Digital Bathymetric Model (DBM) by the European Marine Observation and Data Network (EMODnet). The analyses include hypsometry, volume, descriptive depth statistics, and km-scale seafloor ruggedness, i.e. terrain heterogeneity, for the Baltic Sea as a whole as well as for 17 sub-basins defined by the Baltic Marine Environment Protection Commission (HELCOM). We compare the new EMODnet DBM with 15 IOWTOPO, the previously most widely used DBM of the Baltic Sea which has served as the primary gridded bathymetric resource in physical and environmental studies for nearly two decades. The area of deep water exchange between the Bothnian Sea and the Northern Baltic Proper across the Åland Sea is specifically analysed in terms of depths and locations of critical bathymetric sills. The EMODnet DBM provides a bathymetric sill depth of 88 m at the northern side of the Åland Sea and 60 m at the southern side, differing from previously identified sill depths of 100 and 70 m respectively. High-resolution multibeam 20 bathymetry acquired from this deep water exchange path, where vigorous bottom currents interacted with the seafloor, allows us to assess what we are missing in presently available DBMs in terms of physical characterisation and our ability to then interpret seafloor processes and highlights the need for continued work towards complete high-resolution mapping of the Baltic Sea seafloor.
Evaluation of a Novel Uav-Borne Topo-Bathymetric Laser Profiler
ISPRS - International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, 2016
We present a novel topo-bathymetric laser profiler. The sensor system (RIEGL BathyCopter) comprises a laser range finder, an Inertial Measurement Unit (IMU), a Global Navigation Satellite System (GNSS) receiver, a control unit, and digital cameras mounted on an octocopter UAV (RiCOPTER). The range finder operates on the time-of-flight measurement principle and utilizes very short laser pulses (<1 ns) in the green domain of the spectrum (λ=532 nm) for measuring distances to both the water surface and the river bottom. For assessing the precision and accuracy of the system an experiment was carried out in October 2015 at a pre-alpine river (Pielach in Lower Austria). A 200 m longitudinal section and 12 river cross sections were measured with the BathyCopter sensor system at a flight altitude of 15-20 m above ground level and a measurement rate of 4 kHz. The 3D laser profiler points were compared with independent, quasi-simultaneous data acquisitions using (i) the RIEGL VUX1-UAV lig...
Water Surface Reconstruction in Airborne Laser Bathymetry from Redundant Bed Observations
ISPRS Annals of Photogrammetry, Remote Sensing and Spatial Information Sciences, 2017
In airborne laser bathymetry knowledge of exact water level heights is a precondition for applying run-time and refraction correction of the raw laser beam travel path in the medium water. However, due to specular reflection especially at very smooth water surfaces often no echoes from the water surface itself are recorded (drop outs). In this paper, we first discuss the feasibility of reconstructing the water surface from redundant observations of the water bottom in theory. Furthermore, we provide a first practical approach for solving this problem, suitable for static and locally planar water surfaces. It minimizes the bottom surface deviations of point clouds from individual flight strips after refraction correction. Both theoretical estimations and practical results confirm the potential of the presented method to reconstruct water level heights in dm precision. Achieving good results requires enough morphological details in the scene and that the water bottom topography is cap...