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Published byRuth Perkins Modified over 9 years ago
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Satellite-derived bathymetry (SDB) over the North Slope of Alaska, USA JHC/CCOM NOAA/NOS/OCS/MCD
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Charting Issues with the North Slope 2 (www.nauticalcharts.noaa.gov/mcd/docs /Arctic_Nautical_Charting_Plan.pdf) Images from: Arctic Nautical Charting Plan – a plan to sustainable marine charting transportation in Alaska (Feb. 15, 2013) Barrow, AK Alaska
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Typical North Slope Chart
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Potential solution: satellite imagery 4 Company: DigitalGlobe Swath: 18 km Ground resolution: 2m Organization: NASA/USGS program Swath: 185km Ground resolution: 28.5m Launch Date: 4/1999Launch Date: 10/2009Launch Date: 2/2013 Landsat 7Landsat 8 (LDCM)WorldView2 (Images from landsat.gsfc.nasa.gov and www.digitalglobe.com)
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http://earthexplorer.usgs.gov/ Landsat 7 imagery (1999-2000) Canada U.S.A Coverage (Landsat imagery)
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SDB: Technical overview Approaches: Analytical (utilized by SHOM) Optimization (utilized by UKHO, SHOM, NOAA, and NGA) Look-up tables (LUT) (utilized by ONR and NGA) 6 L obs (λ i ), L obs (λ j )-radiance values m o - gain m 1 - offset Stumpf et al. 2003 NOAA/NOS/OCS/MCD
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7 Arctic waters versus Caribbean waters Barrow, AK Cape Ann, MA Site: Plum Island Water: moderately Clear Bottom: Sand and rock Barrow, AK Site: Elson Lagoon Water: Turbid Bottom: mud, sand and gravel
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Cape Ann, MA RGB composite image collected on 09/27/00 at 1516 before the end of the flood tide 8 Extract of Chart 13278Landsat Image
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Blue Infrared 9 Green
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Correlation of Algorithm Result to Chart Depth BathymetrySediment plumeOptical deep waters R 2 = 0.04R 2 = 0.37 R 2 = 0.77 10 6 m Extinction depth R 2 = 0.77
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http://earthexplorer.usgs.gov/ Landsat 7 imagery (1999-2000) Canada U.S.A However, …
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Reference depth measurements 12 Digitized soundings
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Landsat 7 results (Acquisition date : July 18, 2002) Extinction depth: 4.5 m (15 ft) 60 km30150 4.5 m 0 m Turbidity? Ice
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WV-2 results (Acquisition date: July 21, 2010 through August 10, 2010) Extinction depth: 3.9 m (13 ft) Extinction depth: 4.3 m (14 ft) Turbidity? 9 km 18 km
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Chart 16082 (Scale 1:47,943) NOAA Chart 16081 (scale 1:48,149) Comparison to the chart soundings (WV-2) Absolute depth difference ±6 m 0 m
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16 Bathymetry difference between two satellite images Absolute depth difference ±6 m 0 m Potential solution: time series
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Scatter plots of the differences (WV-2) 17 Statistics ( 4.3 m ): Mean = -0.95 m Standard deviation = 0.81 m Statistics ( 4.3 m ): Mean = -0.49 m Standard deviation = 0.64 m Extinction Depth (4.3 m)
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September 06, 2002 August 15, 2000 August 31, 2000August 11, 2013 Multiple image procedure (Landsat 8)
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Histogram Matching Reference image (September 06, 2002). Original histogram (August 11, 2013)Matched histogram (August 11, 2013) 1. The histograms of the other images were matched to the reference histogram. Mean: 1.1211 Standard deviation: 0.0269 Mean: 1.1211 Standard deviation: 0.0269Mean: 1.0136 Standard deviation: 0.0041
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Difference images (algorithm results) 2. Areas with small difference values (minor changes) between the different images were extracted for further processing. 3. Also, polygon shapefile feature of the extracted areas were generated (manually) based on the density of the available area for further processing.
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Merging all pairs into one dataset 4. Six dataset were produced from the four available images (three pairs). All the dataset were merged into one dataset. 5. The data set was referenced to the chart datum. Sep 06, 2002 – Aug 15, 2000 Sep 06, 2002 – Aug 11, 2013 Sep 06, 2002 – Aug 31, 2000 Aug 15, 2000 – Aug 31, 2000 Aug 15, 2000– Aug 11, 2013 Aug 31, 2000– Aug 11, 2013
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Final result Bathymetry derived from Landsat 7 and Landsat 8 imagery over the north slopes
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Statistical analysis Extinction Depth (4.3 m)
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Incorporating (Summer) 2014 Landsat 8 imagery in order to increase the coverage of the area. Comparison of SDB depth estimates to NOAA Charts – Identify apparent chart discrepancies – Target areas for field work Focus resources to areas of interest (e.g., WV-2). Investigate other promising applications in US waters. – Highly changeable areas – Challenging survey environments Next steps
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Thank you (Left) IR Landsat 7 image (Oct. 3, 2001) showing the ice formation over the suspected shoal. (Right) Satellite-derived bathymetry from WV-2 (August 10, 2010). (Based on Nghiem et al., 2012 approach)
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Final result WV-2 Bathymetry derived from Landsat 7 and Landsat 8 imagery over the north slopes
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