Satellite-derived bathymetry (SDB)over the North Slope of Alaska, USA

JHC/CCOMNOAA/NOS/OCS/MCD

2

Charting Issues with the North Slope

(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

Typical North Slope Chart

4

Potential solution: satellite imagery

Company: DigitalGlobeSwath: 18 kmGround resolution: 2m

Organization: NASA/USGS programSwath: 185kmGround resolution: 28.5m

Launch Date: 4/1999 Launch Date: 10/2009Launch Date: 2/2013

Landsat 7 Landsat 8 (LDCM) WorldView2

(Images from landsat.gsfc.nasa.gov and www.digitalglobe.com)

http://earthexplorer.usgs.gov/

Landsat 7 imagery (1999-2000)

CanadaU.S

.A

Coverage (Landsat imagery)

SDB: Technical overviewApproaches: • Analytical (utilized by SHOM)

• Optimization (utilized by UKHO, SHOM, NOAA, and NGA)

• Look-up tables (LUT) (utilized by ONR and NGA)

6

10 )(ln

)(lnm

L

LmZ

jobs

iobs

Lobs(λi), Lobs(λj)-radiance values

mo- gain m1- offset

Stumpf et al. 2003

NOAA/NOS/OCS/MCD

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Arctic waters versus Caribbean waters

Barrow, AK

Cape Ann, MA

Cape Ann, MASite: Plum IslandWater: moderately ClearBottom: Sand and rock

Barrow, AKSite: Elson LagoonWater: TurbidBottom: 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

Extract of Chart 13278 Landsat Image

9

¯

Blue

Infrared

Green

Correlation of Algorithm Result to Chart Depth

-50.00 -45.00 -40.00 -35.00 -30.00 -25.00 -20.00 -15.00 -10.00 -5.00 0.001.11

1.12

1.13

1.14

1.15

1.16

1.17

Chart Depth (m)

Ratio

ofL

n bl

ue/L

n g

reenBathymetrySediment plumeOptical deep waters

R2= 0.04 R2= 0.37

R2= 0.77

10

6 mExtinction

depth

R2= 0.77

http://earthexplorer.usgs.gov/

Landsat 7 imagery (1999-2000)

CanadaU.S

.A

However, …

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Reference depth measurements

Digitized soundings

Landsat 7 results (Acquisition date : July 18, 2002)

Extinction depth: 4.5 m (15 ft)

60 km30150

4.5 m

0 m

Turbidity?Ice

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

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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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)

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)

September 06, 2002 August 15, 2000

August 31, 2000 August 11, 2013

Multiple image procedure (Landsat 8)

Histogram MatchingReference 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: 1.1211Standard deviation: 0.0269

Mean: 1.1211 Standard deviation: 0.0269Mean: 1.0136 Standard deviation: 0.0041

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.

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

Final result

Bathymetry derived from Landsat 7 and Landsat 8 imagery over the north slopes

Statistical analysisExtinction Depth (4.3 m)

• 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

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)