Nearshore depth derivation using World View-2 multispectral satellite imagery

Julia Ehses & Russell Watkins PIFSC/CRED

Pacific Island Region

Initial Study Site

Image Preprocessing – Three steps are performed before deriving depths.

Step 1Data conversion - Digital number values are converted to top‐of‐atmosphere radiance/reflectance.

Step 2Masking - Non-aquatic and terrestrial areas including clouds, turbidity, breaking surf, and boats are removed from the image by creating an ocean mask.

Step 3Sea Surface corrections - Correction of sun glint in visible bands.

Depth Derivation Method

1. Lyzenga's multiple linear regression analysis

2. Stumpf’s ratio method

ResultsLiDAR

Lyzenga

Stumpf

Lyzenga Stumpf

Final Products are available for download at:

http://www.soest.hawaii.edu/pibhmc/pibhmc_mapping.htm

Products

Conclusions

• WV-2 multispectral satellite imagery can be used to derive depths in water shallower than 20m.

• Best results are obtained over steep slopes and homogenous hard bottom.

• Shallow sandy substrate can lead to false depth values and reversed topography.

• Site-specific method modification is often required.

• Results are highly dependant upon the availability of quality ground control data and satellite imagery.

Image Acquisition

Questions?

Julia.Ehses@noaa.gov

Russel.Watkins@noaa.gov

The 8 spectral bands of WorldView-2