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Ship Draft Detection Based on
Machine VisionRAN Xin, SHI Chaojian, XIAO Baojia
Merchant Marine College, Shanghai Maritime
University, Shanghai, P.R. China2012-10-2
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1 Introduction
Water-borne vesselscan carry largeamounts of cargo
economically It is important to
obtain accuratereadings of the vesseldraft to determine the
amount of cargo thathas been loaded ontothe vessel.
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1 Introduction
The ship draft marksare located at 6specific positionsaround the freeboard.
The marine surveyorswill observe the draftlines and read thenumbers before andafter unloading
cargoes, then usethem to calculate theweight of cargoes.
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1 Introduction
Limits of draftsurvey by manualobservation
Subjective visualestimation leads todifferent results
Conditions onoceans and riverscan drasticallyaffect the draft linemeasurements
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2 Draft survey by machine vision
undetected
detected
Preprocessing
Draft line detection
enhancement
Ship draft calculation
Original ship draft image
Draft mark recognition
Image acquisition
Recognition
Result statistic and display
Draft detection
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2.1 Image acquisition
The original images are taken by surveyor around the ship using camera,then the image data are transferred to the computer to process.
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2.1 Image acquisition
Usually not suitable for direct detection of draft line due toinappropriate position or view angle of surveyor, and also due to theinfluence of sunshine or wave conditions.
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2.2 Image preprocessing
The red, green and blue channel are divided from theoriginal image. It is noticed that the draft line is moredistinct in red channel than in other channels.
So the red channel will be split from the original imageand used at the subsequently step.
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2.3 Edge detection
The results illustrate that the best way to extractingdraft line is Canny operator adopted in red imagechannel.
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2.4 Geometry transformation
An affine transform algorithm is used to adjustthe image making the draft line horizontal.
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2.5 Hough transform
The two longer lines, the draft line and theupper waterline, are detected and illustrated ingreen.
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2.6 Draft line detection
Depending on the common sense that the watermarkline is always at upper position than draft line, the lowerand true draft line will be picked out at the final step.
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3. Draft mark recognition
Binarization
Draft mark
extraction
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3. Draft mark recognition continue
Thin algorithmof mathematicalmorphology.
Draft markrecognitionbased ontrigeminal point
features.
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3. Draft mark recognition continue
Draft markcalculation anddisplay.
Draft markstatistic.
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4. Conclusion
Draft line detection is the first and significantstep for ship draft survey.
In order to overcome the limits of the traditionalship draft survey methods, an automaticrecognition system based on machine vision ispresented.
The experimental results show that theproposed system is effective and can be usedinstead of visual observation.
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Thank You!