Difference between revisions of "LiDAR"

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(Created page with "=Quick summary= thumb|250px|Figure 1: - file:adcp_qboat.png|thumb|250px|Figure 2: Teledyne Marine Q-boat of VAW equipped with Riverpro ADCP a...")
 
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=Introduction=
 
=Introduction=
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Acoustic Doppler Current Profiler (ADCP) allows quick, easy and accurate measurements of 3D velocity time series and bathymetry, and computation of discharges in rivers, estuaries, lakes and reservoirs as well as oceans. ADCP data can be used for calibration of numerical models, hydraulic studies (for example, flow field around hydraulic structures), habitat quality assessment and modelling, hydro-morphologic surveys and sediment studies.
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Lidar is a measurement technique that measures the distance from a georeferenced laser sensor to a ground target by illuminating the target with the pulsed light (Figure 66). The sensor detects the reflected pulses. The time shifts in laser return and wavelengths can then be used to make digital 3-D representations of the target areas, e.g. a river section. The laser pulses can have different wavelengths, most commonly red and green.  
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The ADCP is equipped with multi-beams (three up to nine beams, Figure 1), which emit acoustic energy at a known frequency and record the frequency of the acoustic energy backscattered by the particles in the water column. The velocity of the water flow along each beam is computed based on the change in the frequency of the emitted and backscattered acoustic energy, i.e. the Doppler shift. Detailed information on the ADCP working principle and its limitations are described by Simpson (2002). The ADCP beams are positioned to 20 or 30 degree away from the vertical axis. By using a simple trigonometry, 3D velocity components are computed from the Doppler shifts measured with three or four sonar beams. In the latter, a redundant, fourth beam is used to compute error
 
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velocity, which is the difference between a velocity measured by one set of three beams and a velocity measured by another set of three beams at the same time (Simpson, 2002). The error velocity is used to evaluate the assumption of horizontal homogeneity. The frequency of the ultrasonic sound transmitted by commercially available ADCPs ranges from 30 kHz to 3000 KHz (Simpson, 2002). ADCP can be used at a fixed position, i.e. stationary, or mounted to a tethered boat, manned boat or a remote-controlled boat (Mueller et al., 2013). Non-stationary i.e. moving boat ADCP measurements yield the flow velocity and direction relative to the boat and hence the velocity of the boat should be accounted for by using either bottom tracking or global positioning system (GPS) to determine true flow velocity.  
 
  
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The red laser is more common and therefore cheaper. However, other than the NeoDyn Yag laser it can not penetrate the water surface. Therefore the green laser (wavelength 532nm) is most preferred in scientific and especially river related measurements (Figure 67). However, a certain distance from the source of the light to the eye of any person passing accidentally the measurement must be guaranteed due to safety reasons. This is usually not a problem, as this application is used for large scale approached, mainly with so called Airborne Laser Scanning (ALS) where the laser is mounted to a small plane, a helicopter or even a large (more than 15 kg load) drone.
  
 
=Application=
 
=Application=
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Within the scope of FIThydro, high resolution 3D velocity, as well as bathymetry measurements, have been conducted using an ADCP mounted on a high speed remote-controlled boat at two hydropower plants (HPP) in Switzerland since the beginning of 2018. The models of the ADCP and the boat are River Pro 1200 kHz including piston style four-beam transducer with a 5th, independent 600 kHz vertical beam and Q-Boat purchased from Teledyne Marine, USA, respectively (Figure 2). An external Differential GPS (DGPS) system from A326 AtlasLink (Hemisphere) was used to accurately measure the positions of the ADCP. One set of the battery for the Q-boat allowed us to make measurements for 4 hours up to 10 hours depending on the flow velocity and field conditions i.e. temperature.
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As the laser and also the plane or helicopter are a quite expensive set of devices, the measurements are usually taken by private contractors. Most of the time the client is a municipality, the government or a hydropower operator interested in the geometry of floodplains and the bathymetry of rivers.  
  
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Compass calibration and moving bed tests are conducted before each ADCP measurement at the case study HPPs. The Test Case study HPP Schiffmühle is located on the 35 km long river Limmat between in Untersiggenthal and Turgi near Baden in Switzerland (see the Test Case presentation file for HPP Schiffmühle). Two transects of ADCP at each densely spaced cross-section along the river were enough but high accuracy of altitude data was required for the bathymetry measurements at the HPP and in general. The present DGPS system resulted in ±1m of errors in altitude measurements (Figure 3, black line). Therefore, use of a total station, which is time consuming, or real-time kinematic (RTK) GPS is recommended to accurately determine water surface and hence bathymetry (Figure 3, red line from total station measurements).  
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In Norway, most of the rivers are currently measured with a red laser (hence no underwater registrations). These are relatively easily available for research institutions through public website hoydedata.no. Also available at the website are green laser derived bathymetry of a selection of river reaches.
  
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Furthermore, the test results from the HPP Bannwil located on River Aare in canton Bern indicated that averaging of at least 8 transects or even more at each cross-section is needed to obtain robust and smooth velocity field and accurate discharge data at highly turbulent and 3D flows occurring in rivers, turbine inlet and outlets or other hydraulic structures (see the Test Case presentation file for HPP Bannwil).
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The penetration depth of the green laser through water depends highly on turbidity, flow velocity, reflections on the surface / waves and water depth. It also depends most probably on the type of suspended load. Thus, green laser measurements are in many cases supplied with echosounding data.
  
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The ADCP data from both HPPs Schiffmühle and Bannwil are post-processed according to the workflow sketched in Figure 4 using the software WinRiver II (Teledyne software) and velocity mapping toolbox (VMT, Matlab based software for processing and visualizing ADCP data provided by U.S. Geological Survey). Figure 5 shows the depth-averaged velocities at the HPP Bannwil plotted with VMT. VMT can be used with the output files from Sontek ADCPs. For further data analysis and presentation on the maps like river bed changes, Q-GIS (free software) or ARC-GIS (Commercial software) are also recommended.
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Problems can also be caused by any other overlap of objects such as trees above ground or submerged vegetation above river bottoms (Figure 68). This can lead to blurred areas and various z-data (height marker) for the same x/y coordinates.
  
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The present system based on the remote-controlled boat platform has advantages over the tethered boat ADCP application. These are less man-power needed, faster and more measurements in a shorter time, no flow disturbance and interference with beams and smoother movement of the boat.
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The measurements generate a point cloud. Post-processing is usually done in a specific software (also freeware) as is the case many other applications (such as SfM). However, as it is a usual output format, it is not a specific part of the Lidar system.
  
  
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=Relevant literature=
 
=Relevant literature=
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*Mueller, D.S., Wagner, C.R., Rehmel, M.S., Oberg, K.A., Rainville, F. (2013). Measuring discharge with acoustic Doppler current profilers from a moving boat (ver. 2.0, December 2013), U.S. Geological Survey Techniques and Methods, book 3, chap. http://dx.doi.org/10.3133/tm3A22.
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*Bizzi, S., Demarchi, L., Grabowski, R.C., Weissteiner, C.J., Van de Bund, W., 2016. The use of remote sensing to characterise hydromorphological properties of European rivers. Aquatic Sciences 78, 57–70. https://doi.org/10.1007/s00027-015-0430-7
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*Brock, J.C., Purkis, S.J., 2009. The Emerging Role of Lidar Remote Sensing in Coastal Research and Resource Management. Journal of Coastal Research 10053, 1–5. https://doi.org/10.2112/SI53-001.1
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*Brock und Purkis - 2009 - The Emerging Role of Lidar Remote Sensing in Coast.pdf, n.d.
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*Costa, B.M., Battista, T.A., Pittman, S.J., 2009. Comparative evaluation of airborne LiDAR and ship-based multibeam SoNAR bathymetry and intensity for mapping coral reef ecosystems. Remote Sensing of Environment 113, 1082–1100. https://doi.org/10.1016/j.rse.2009.01.015
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*Costa et al. - 2009 - Comparative evaluation of airborne LiDAR and ship-.pdf, n.d.
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*Gao, J., 2009. Bathymetric mapping by means of remote sensing: methods, accuracy and limitations. Progress in Physical Geography 33, 103–116. https://doi.org/10.1177/0309133309105657
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*Hilldale, R.C., Raff, D., 2008. Assessing the ability of airborne LiDAR to map river bathymetry. Earth Surface Processes and Landforms 33, 773–783. https://doi.org/10.1002/esp.1575
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*Hilldale und Raff - 2008 - Assessing the ability of airborne LiDAR to map riv.pdf, n.d.
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*Irish, J.L., White, T.E., 1998. Coastal engineering applications of high-resolution lidar bathymetry. Coastal Engineering 35, 47–71. https://doi.org/10.1016/S0378-3839(98)00022-2
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*Kinzel, P.J., Legleiter, C.J., Nelson, J.M., 2013. Mapping River Bathymetry With a Small Footprint Green LiDAR: Applications and Challenges : Mapping River Bathymetry with a Small Footprint Green LiDAR: Applications and Challenges. JAWRA Journal of the American Water Resources Association 49, 183–204. https://doi.org/10.1111/jawr.12008
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Langhammer, J., Janský, B., Kocum, J., Minařík, R., 2018a. 3-D reconstruction of an abandoned montane reservoir using UAV photogrammetry, aerial LiDAR and field survey. Applied Geography 98, 9–21. https://doi.org/10.1016/j.apgeog.2018.07.001
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*Langhammer, J., Janský, B., Kocum, J., Minařík, R., 2018b. 3-D reconstruction of an abandoned montane reservoir using UAV photogrammetry, aerial LiDAR and field survey. Applied Geography 98, 9–21. https://doi.org/10.1016/j.apgeog.2018.07.001
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*Lejot, J., Delacourt, C., Piégay, H., Fournier, T., Trémélo, M.-L., Allemand, P., 2007. Very high spatial resolution imagery for channel bathymetry and topography from an unmanned mapping controlled platform. Earth Surface Processes and Landforms 32, 1705–1725. https://doi.org/10.1002/esp.1595
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*Lükő, G., Rüther, D.N., n.d. UAV BASED HYDROMORPHOLOGICAL MAPPING OF A RIVER REACH TO IMPROVE HYDRODYNAMIC NUMERICAL MODELS 1.
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*Lükő, G., Rüther, D.N., n.d. UAV Based Hydromorphological Mapping of a River Reach to Improve Hydrodynamic Numerical Models.
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*Marcus, W.A., Fonstad, M.A., 2008. Optical remote mapping of rivers at sub-meter resolutions and watershed extents. Earth Surface Processes and Landforms 33, 4–24. https://doi.org/10.1002/esp.1637
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*Mallet C., 2010; LIDAR aéroportéstopographiques & bathymétriques ; https://www.umr-cnrm.fr/ecole_lidar/IMG/pdf/Mallet-Topo_Bathy_Veget.pdf
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*Saylam, K., Brown, R.A., Hupp, J.R., 2017. Assessment of depth and turbidity with airborne Lidar bathymetry and multiband satellite imagery in shallow water bodies of the Alaskan North Slope. International Journal of Applied Earth Observation and Geoinformation 58, 191–200. https://doi.org/10.1016/j.jag.2017.02.012
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*Wang, C.-K., Philpot, W.D., 2007. Using airborne bathymetric lidar to detect bottom type variation in shallow waters. Remote Sensing of Environment 106, 123–135. https://doi.org/10.1016/j.rse.2006.08.003
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*Wang und Philpot - 2007 - Using airborne bathymetric lidar to detect bottom .pdf, n.d.
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*Zhang, K., Yang, F., Zhang, H., Su, D., Li, Q., 2017. Morphological characterization of coral reefs by combining lidar and MBES data: A case study from Yuanzhi Island, South China Sea: MORPHOLOGICAL STUDY OF CORAL REEF. Journal of Geophysical Research: Oceans 122, 4779–4790. https://doi.org/10.1002/2016JC012507
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*Zhang, K., Frey, H.C., 2006. Road Grade Estimation for On-Road Vehicle Emissions Modeling Using Light Detection and Ranging Data. Journal of the Air & Waste Management Association 56, 777–788. https://doi.org/10.1080/10473289.2006.10464500
  
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*Simpson, M.R. (2002). Discharge measurements using a broadband acoustic Doppler current profiler. Open-file Report 2001-1, https://doi.org/10.3133/ofr011.
 
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<b>Links to the suppliers of equipment:</b>
 
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*Teledyne Marine, ADCP RiverPro: http://www.teledynemarine.com/riverpro-adcp?ProductLineID=13
 
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*Teledyne Marine, Q-Boat: http://www.teledynemarine.com/Lists/Downloads/Q-Boat_1800_Datasheet.pdf
 
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*Hemisphere Atlas DPS: https://hemispheregnss.com/Atlas/atlaslinke284a2-gnss-smart-antenna-1226
 
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*Sontek ADCP M9: https://www.sontek.com/riversurveyor-s5-m9
 
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<b>Software for ADCP data analysis:</b>
 
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*Velocity Mapping Toolbox: https://hydroacoustics.usgs.gov/movingboat/VMT/VMT.shtml
 
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*Q-GIS: https://qgis.org/en/site/
 
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*ARC-GIS: https://www.esri.com/en-us/arcgis/about-arcgis/overview
 
  
 
=Contact information=
 
=Contact information=

Revision as of 10:04, 19 June 2019

Quick summary

Figure 1: -
Figure 2: Teledyne Marine Q-boat of VAW equipped with Riverpro ADCP and DGPS.
Figure 3: Water surface elevation along the power canal of HPP Schiffmühle (black line: DGPS data and red line: total station data).
Figure 4: Workflow used for post-processing of ADCP data (click to expand).
Figure 5:

Developed by:

Date:

Type: Device, Tool

Suitable for the following [[::Category:Measures|measures]]:

Introduction

Lidar is a measurement technique that measures the distance from a georeferenced laser sensor to a ground target by illuminating the target with the pulsed light (Figure 66). The sensor detects the reflected pulses. The time shifts in laser return and wavelengths can then be used to make digital 3-D representations of the target areas, e.g. a river section. The laser pulses can have different wavelengths, most commonly red and green.

The red laser is more common and therefore cheaper. However, other than the NeoDyn Yag laser it can not penetrate the water surface. Therefore the green laser (wavelength 532nm) is most preferred in scientific and especially river related measurements (Figure 67). However, a certain distance from the source of the light to the eye of any person passing accidentally the measurement must be guaranteed due to safety reasons. This is usually not a problem, as this application is used for large scale approached, mainly with so called Airborne Laser Scanning (ALS) where the laser is mounted to a small plane, a helicopter or even a large (more than 15 kg load) drone.

Application

As the laser and also the plane or helicopter are a quite expensive set of devices, the measurements are usually taken by private contractors. Most of the time the client is a municipality, the government or a hydropower operator interested in the geometry of floodplains and the bathymetry of rivers.

In Norway, most of the rivers are currently measured with a red laser (hence no underwater registrations). These are relatively easily available for research institutions through public website hoydedata.no. Also available at the website are green laser derived bathymetry of a selection of river reaches.

The penetration depth of the green laser through water depends highly on turbidity, flow velocity, reflections on the surface / waves and water depth. It also depends most probably on the type of suspended load. Thus, green laser measurements are in many cases supplied with echosounding data.

Problems can also be caused by any other overlap of objects such as trees above ground or submerged vegetation above river bottoms (Figure 68). This can lead to blurred areas and various z-data (height marker) for the same x/y coordinates.

The measurements generate a point cloud. Post-processing is usually done in a specific software (also freeware) as is the case many other applications (such as SfM). However, as it is a usual output format, it is not a specific part of the Lidar system.


Other information

The total costs for the geophone and accelerometer sensors amount to approx. 885-1'330 €. The costs for the field computer, the analog-digital-converter, and the 3G modem are approx. 5'300-6'200 €. The total costs for the Teledyne RiverPro 1200 kHz, Teledyne Q-boat and DGPS from Hemisphere Atlas link amount to approx. 22’000 €, 21’200 € and 3’340 € respectively. The costs of shipping, VAT, some mounting apparatus and long-range radio modem are excluded. For current costs of the equipment, we recommend to ask the corresponding supplier. Note that Q-boat can also house Sontek RiverSurveyor M9. Furthermore, a rugged laptop for field use is recommended.

Relevant literature

  • Bizzi, S., Demarchi, L., Grabowski, R.C., Weissteiner, C.J., Van de Bund, W., 2016. The use of remote sensing to characterise hydromorphological properties of European rivers. Aquatic Sciences 78, 57–70. https://doi.org/10.1007/s00027-015-0430-7
  • Brock, J.C., Purkis, S.J., 2009. The Emerging Role of Lidar Remote Sensing in Coastal Research and Resource Management. Journal of Coastal Research 10053, 1–5. https://doi.org/10.2112/SI53-001.1
  • Brock und Purkis - 2009 - The Emerging Role of Lidar Remote Sensing in Coast.pdf, n.d.
  • Costa, B.M., Battista, T.A., Pittman, S.J., 2009. Comparative evaluation of airborne LiDAR and ship-based multibeam SoNAR bathymetry and intensity for mapping coral reef ecosystems. Remote Sensing of Environment 113, 1082–1100. https://doi.org/10.1016/j.rse.2009.01.015
  • Costa et al. - 2009 - Comparative evaluation of airborne LiDAR and ship-.pdf, n.d.
  • Gao, J., 2009. Bathymetric mapping by means of remote sensing: methods, accuracy and limitations. Progress in Physical Geography 33, 103–116. https://doi.org/10.1177/0309133309105657
  • Hilldale, R.C., Raff, D., 2008. Assessing the ability of airborne LiDAR to map river bathymetry. Earth Surface Processes and Landforms 33, 773–783. https://doi.org/10.1002/esp.1575
  • Hilldale und Raff - 2008 - Assessing the ability of airborne LiDAR to map riv.pdf, n.d.
  • Irish, J.L., White, T.E., 1998. Coastal engineering applications of high-resolution lidar bathymetry. Coastal Engineering 35, 47–71. https://doi.org/10.1016/S0378-3839(98)00022-2
  • Kinzel, P.J., Legleiter, C.J., Nelson, J.M., 2013. Mapping River Bathymetry With a Small Footprint Green LiDAR: Applications and Challenges : Mapping River Bathymetry with a Small Footprint Green LiDAR: Applications and Challenges. JAWRA Journal of the American Water Resources Association 49, 183–204. https://doi.org/10.1111/jawr.12008

Langhammer, J., Janský, B., Kocum, J., Minařík, R., 2018a. 3-D reconstruction of an abandoned montane reservoir using UAV photogrammetry, aerial LiDAR and field survey. Applied Geography 98, 9–21. https://doi.org/10.1016/j.apgeog.2018.07.001

  • Langhammer, J., Janský, B., Kocum, J., Minařík, R., 2018b. 3-D reconstruction of an abandoned montane reservoir using UAV photogrammetry, aerial LiDAR and field survey. Applied Geography 98, 9–21. https://doi.org/10.1016/j.apgeog.2018.07.001
  • Lejot, J., Delacourt, C., Piégay, H., Fournier, T., Trémélo, M.-L., Allemand, P., 2007. Very high spatial resolution imagery for channel bathymetry and topography from an unmanned mapping controlled platform. Earth Surface Processes and Landforms 32, 1705–1725. https://doi.org/10.1002/esp.1595
  • Lükő, G., Rüther, D.N., n.d. UAV BASED HYDROMORPHOLOGICAL MAPPING OF A RIVER REACH TO IMPROVE HYDRODYNAMIC NUMERICAL MODELS 1.
  • Lükő, G., Rüther, D.N., n.d. UAV Based Hydromorphological Mapping of a River Reach to Improve Hydrodynamic Numerical Models.
  • Marcus, W.A., Fonstad, M.A., 2008. Optical remote mapping of rivers at sub-meter resolutions and watershed extents. Earth Surface Processes and Landforms 33, 4–24. https://doi.org/10.1002/esp.1637
  • Mallet C., 2010; LIDAR aéroportéstopographiques & bathymétriques ; https://www.umr-cnrm.fr/ecole_lidar/IMG/pdf/Mallet-Topo_Bathy_Veget.pdf
  • Saylam, K., Brown, R.A., Hupp, J.R., 2017. Assessment of depth and turbidity with airborne Lidar bathymetry and multiband satellite imagery in shallow water bodies of the Alaskan North Slope. International Journal of Applied Earth Observation and Geoinformation 58, 191–200. https://doi.org/10.1016/j.jag.2017.02.012
  • Wang, C.-K., Philpot, W.D., 2007. Using airborne bathymetric lidar to detect bottom type variation in shallow waters. Remote Sensing of Environment 106, 123–135. https://doi.org/10.1016/j.rse.2006.08.003
  • Wang und Philpot - 2007 - Using airborne bathymetric lidar to detect bottom .pdf, n.d.
  • Zhang, K., Yang, F., Zhang, H., Su, D., Li, Q., 2017. Morphological characterization of coral reefs by combining lidar and MBES data: A case study from Yuanzhi Island, South China Sea: MORPHOLOGICAL STUDY OF CORAL REEF. Journal of Geophysical Research: Oceans 122, 4779–4790. https://doi.org/10.1002/2016JC012507
  • Zhang, K., Frey, H.C., 2006. Road Grade Estimation for On-Road Vehicle Emissions Modeling Using Light Detection and Ranging Data. Journal of the Air & Waste Management Association 56, 777–788. https://doi.org/10.1080/10473289.2006.10464500


Contact information

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