An Effective Camera Based Water level recording Technology for ...
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Dr.-Ing. Issa Hasan SEBA Hydrometrie GmbH & Co. KG An Effective Camera Based Water level recording Technology for Flood Monitoring I. Hasan 1 , M. Satzger 1 , M. Sattler 1 , R. Duester 1 , T. Hies 2 , E. Jose 2 1 SEBA Hydrometrie GmbH & Co. KG, Gewerbestr. 61A, 87600 Kaufbeuren, Germany 2 DHI Water & Environment (S) Pte Ltd, Singapore Contact: [email protected] Flood risk management has an increasing importance in many areas of the world, especially under the consideration of the potential influence of climate change and the reduction of natural river meadows caused by human activities. Therefore, an effective and timely monitoring of surface water level is a very crucial factor of the quantitative flood risk management for the reduction of potential damages. A further development of the camera based product line is the DischargeKeeper, which is a new innovation for non-contact continuous discharge measuring without flow tracers. Using the Particle Image Velocimetry method, the surface velocity flow is obtained. For the vertical velocity profiling a roughness dependent model is applied. The water level, velocity and discharge parameters are obtained at the end of the optical measurement. The aim of the present work is to develop a new effective method for a continuous contactless water level measurement even under critical conditions like floods and hydraulic jumps, under which other localized gauging methods could be temporal out of operation or not sufficiently representative. In particular, the access to images of the site, which are the basis of the new water level detection method, will allow investigating the situation and judging on the quality of the water level measurement. The image processing and, as a result, the obtaining of water level data should be occur on site. Day & night HD-camera Method and Materials SEBA Hydrometrie GmbH& Co. KG has developed a new gauge for enhanced water level detection by image processing. The new instrument for optical water level measurement is called GaugeKeeper and is based on the edge detection principle, together with a detection algorithm which runs in real-time on the device. As it is shown in the Figure 1, the GaugeKeeper system consists of the following components: day and night time camera, infrared projector, white board, processor unit, data logger and a data transmission unit. The data logging, processing and transmission units are all integrated into one compact system. However, it is also possible to apply only the GaugeKeeper-Algorithm to an existing system (e.g. an installed camera). Alarm limits can be defined for cases when water levels reach pre-defined critical limits or the gauging equipment updates the user with hardware status warnings. Fig.1: GaugeKeeper components and an on-site picture of the installed system Fig.2: Water level detection for an image captured by the day-camera (left: original image, right: transformed image) Fig.3: Water level detection for an image captured by the night-camera (left: original image, right: transformed image) The outline steps for the robust detection of the water level • Automatic, adaptive selection of the region-of-interest (ROI); • An image processing technique, the so-called edge detection, is applied to obtain the edge image of the ROI image edge-detection assuming discontinuities of intensities of pixels of images are linked to physical changes e.g. material changes, depth changes, surface orientation changes etc. (Barrow et al., 1981), (Lindeberg, 2001), (Jaehne, 2002); • Hough-transformation calculating the longest straight line in the edge image of the water level (the red line). Figure 2 and 3 show the transformation of the (original / un-processed) captured images to undistorted frontal-view images with the region of interest and red line indicating the water level. After the water level is detected through the above methods, the water depth of the channel is interpolated based on the field measurement done at the ROI Conclusions and key features The developed system was verified and validated under various weather and lighting conditions. The presented Technology can provide a real-time overview about the observed sites. Due to the optical image processing method, the GaugeKeeper can work even in extreme events such as floods. Silting or flotsam have no influence on the operation of GaugeKeeper. Very low level of maintenance necessary. The GaugeKeeper informs you immediately by SMS and/ or e-mail when critical system states are reached. The low energy consumption allows a permanent autonomous battery or solar operation. The system has analogue or Modbus or SDI12 outputs. Connections for additional sensors and webcams are possible. The activation of the measuring system can alternatively be controlled by trigger pulses. Fig.6: optical discharge measuring by means of the DischargeKeeper Results and discussion The developed optical gauge was tested at several sites and under different environmental conditions (rain and heavy tropical rain events, snow, fog, day and night) in Germany and Singapore. The validation was carried out by comparing the water levels determined by the new developed gauge against the levels measured by conventional sensors like radar and pressure sensors at the same location. The data agreement between the measurements carried out by the optical gauge and by the two reference sensors was very good (Fig. 4 and 5). The accuracy of the camera system was 1.1 % for the test period between April and December 2011. A second test, with a pressure sensor as a reference gauge, was carried out in the period between December 2014 and February 2015. The relative deviation was in this case around 0.95 % and the root-mean-square error (RMSE) was about 1 cm (the average water depth of the site was around 76 cm). 0 50 100 150 200 250 01.12.2014 11.12.2014 21.12.2014 31.12.2014 10.01.2015 20.01.2015 30.01.2015 Waterlevel [cm] Time Water level measurement comparison plot pressure sensor_waterlevel GaugeKeeper_camera waterlevel 100 100,2 100,4 100,6 100,8 101 101,2 101,4 101,6 101,8 102 26.04.2011 15:54 26.04.2011 17:49 26.04.2011 19:45 26.04.2011 21:40 Water Level [m] Time Water level measurement comparison plot Radar Water Level GaugeKeeper-camera water level Fig. 4: Water level measurement comparison between GaugeKeeper and a radar sensor at a site in Singapore Fig. 5: Water level measurement comparison between GaugeKeeper and a pressure sensor at a site in Germany
Transcript of An Effective Camera Based Water level recording Technology for ...
Dr.-Ing. Issa HasanSEBA Hydrometrie GmbH & Co. KG
An Effective Camera Based Water level recording Technology for Flood Monitoring
I. Hasan1, M. Satzger1, M. Sattler1, R. Duester1, T. Hies2, E. Jose2
1SEBA Hydrometrie GmbH & Co. KG, Gewerbestr. 61A, 87600 Kaufbeuren, Germany2DHI Water & Environment (S) Pte Ltd, Singapore
Contact: [email protected]
Flood risk management has an increasing importance in many areas of the world, especially under theconsideration of the potential influence of climate change and the reduction of natural river meadowscaused by human activities. Therefore, an effective and timely monitoring of surface water level is a verycrucial factor of the quantitative flood risk management for the reduction of potential damages.
A further development of the camera based product line is the
DischargeKeeper, which is a new innovation for non-contact
continuous discharge measuring without flow tracers. Using the Particle
Image Velocimetry method, the surface velocity flow is obtained.For the vertical velocity profiling a roughness dependent model is applied.The water level, velocity and discharge parameters are obtained at theend of the optical measurement.
The aim of the present work is to develop a new effective method for a continuous contactless water levelmeasurement even under critical conditions like floods and hydraulic jumps, under which other localizedgauging methods could be temporal out of operation or not sufficiently representative. In particular, theaccess to images of the site, which are the basis of the new water level detection method, will allowinvestigating the situation and judging on the quality of the water level measurement. The imageprocessing and, as a result, the obtaining of water level data should be occur on site.
Day & night HD-camera
Method and Materials
SEBA Hydrometrie GmbH& Co. KG hasdeveloped a new gauge for enhancedwater level detection by image processing.The new instrument for optical water levelmeasurement is called GaugeKeeper andis based on the edge detection principle,together with a detection algorithm whichruns in real-time on the device.
As it is shown in the Figure 1, theGaugeKeeper system consists of thefollowing components: day and night timecamera, infrared projector, white board,processor unit, data logger and a datatransmission unit. The data logging,processing and transmission units are allintegrated into one compact system.However, it is also possible to apply onlythe GaugeKeeper-Algorithm to an existingsystem (e.g. an installed camera).
Alarm limits can be defined for cases whenwater levels reach pre-defined criticallimits or the gauging equipment updatesthe user with hardware status warnings.
Fig.1: GaugeKeeper components and an on-site picture of the installed system
Fig.2: Water level detection for an image captured by the day-camera (left: original image, right: transformed image)
Fig.3: Water level detection for an image captured by the night-camera (left: original image, right: transformed image)
The outline steps for the robust detection of the water level
• Automatic, adaptive selection of the region-of-interest (ROI);• An image processing technique, the so-called edge detection, is applied to obtain the edge image
of the ROI image edge-detection assuming discontinuities of intensities of pixels of images arelinked to physical changes e.g. material changes, depth changes, surface orientation changes etc.(Barrow et al., 1981), (Lindeberg, 2001), (Jaehne, 2002);
• Hough-transformation calculating the longest straight line in the edge image of the water level(the red line).
Figure 2 and 3 show the transformation of the (original / un-processed) captured images toundistorted frontal-view images with the region of interest and red line indicating the water level.After the water level is detected through the above methods, the water depth of the channel isinterpolated based on the field measurement done at the ROI
Conclusions and key features
The developed system was verified and validated under various weather and lightingconditions.
The presented Technology can provide a real-time overview about the observed sites.
Due to the optical image processing method, the GaugeKeeper can work even in extremeevents such as floods. Silting or flotsam have no influence on the operation ofGaugeKeeper.
Very low level of maintenance necessary.
The GaugeKeeper informs you immediately by SMS and/ or e-mail when critical systemstates are reached.
The low energy consumption allows a permanent autonomous battery or solaroperation.
The system has analogue or Modbus or SDI12 outputs.
Connections for additional sensors and webcams are possible.
The activation of the measuring system can alternatively be controlled by trigger pulses.
Fig.6: optical discharge measuring by means of the DischargeKeeper
Results and discussion
The developed optical gauge was tested at several sites and under different environmentalconditions (rain and heavy tropical rain events, snow, fog, day and night) in Germany andSingapore. The validation was carried out by comparing the water levels determined by thenew developed gauge against the levels measured by conventional sensors like radar andpressure sensors at the same location. The data agreement between the measurementscarried out by the optical gauge and by the two reference sensors was very good (Fig. 4 and5). The accuracy of the camera system was 1.1 % for the test period between April andDecember 2011. A second test, with a pressure sensor as a reference gauge, was carried outin the period between December 2014 and February 2015. The relative deviation was in thiscase around 0.95 % and the root-mean-square error (RMSE) was about 1 cm (the averagewater depth of the site was around 76 cm).
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Radar Water Level GaugeKeeper-camera water level
Fig. 4: Water level measurement comparisonbetween GaugeKeeper and a radarsensor at a site in Singapore
Fig. 5: Water level measurement comparisonbetween GaugeKeeper and a pressuresensor at a site in Germany
