Bathymetry and Water Column Correction using 4SM – A HyPhoon user success story

This is part of a series on user success stories that showcase applications and accomplishments using HyPhoon datasets. Send us your story!

The Accomplishment: Dr. Yann Morel derived bathymetry and water column corrected reflectance for Heron Reef using his Self-calibrated Supervised Spectral Shallow-sea Modeler (4SM). Output includes water depth, as shown below, and water column corrected reflectance at the seafloor. Both products are being added to the Heron Reef dataset, and will soon be available for the community to download.

4SM Heron Reef

CASI hyperspectral (left) and 4SM derived bathymetry (right)

Data: The source data used for this success story was the 2002 CASI hyperspectral imagery from the Heron Reef dataset provided courtesy of the Center for Spatial Environmental Research at the University of Queensland. Heron Reef is located at the southern end of the Great Barrier Reef in Australia. The imagery has 1 m pixels and a spectral range from 400-800 nm with 19 spectral bands.

4SM Overview: The 4SM model is based on established physical principles of shallow water optics, operates without need for field data or atmospheric correction, and works with both multispectral and hyperspectral imagery. The model assumes both water and atmospheric conditions are uniform throughout the given scene, requires the presence of both deep water and bare land pixels, and is most applicable to clear shallow water at 0-30 meters depth.

At its core, 4SM utilizes a variant of Lyzenga’s method to calculate the slopes for all bi-dimensional band pairs, which are then used to interpolate diffuse attenuation coefficients for all visible bands. Surface glint is minimized using information from a NIR or SWIR band, bare land pixels are used to derive the slope of the soil line and the water volume reflectance, and deep water pixels are used to approximate deep water radiance. All of this information is then combined to drive an optimization approach for estimating water depth.

Output ultimately includes both water depth and water column corrected reflectance, which can both be used for further habitat and geomorphic analyses.

For more on 4SM: http://www.watercolumncorrection.com/

To access HyPhoon data: http://hyphoon.hyspeedcomputing.com/data-sets/

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HyPhoon – Announcing Launch of Geospatial Data Sharing Service

HySpeed computing is proud to announce the release of HyPhoon, a community gateway for the access and exchange of datasets, applications and knowledge.

The inaugural dataset offered through HyPhoon is from Heron Reef, Australia, provided courtesy of the Center for Spatial Environmental Research at the University of Queensland.

Heron ReefHeron Reef (32 km^2) is located at the southern end of the Great Barrier Reef and has been a focus of coral reef research since the early 1900s. The reef contains Heron Island, which hosts one of the longest running, most significant, coral reef research stations in the world. One of the first large scale reef mapping projects in the world was developed on Heron Reef in the 1980s. Since the late 1990s the Biophysical Remote Sensing Group at the University of Queensland has developed and tested remote sensing applications on Heron Reef with collaborators from around Australia and the rest of the world.

Data offered for the Heron Reef dataset currently includes:

  • mosaic of 2002 CASI hyperspectral imagery at 1 m spatial resolution
  • field transects from 2002 of substrate cover for 3,586 photos
  • depth measurements from 2007 for 7,462 individual soundings
  • bathymetric map derived from the 2002 CASI imagery
  • habitat map derived from 2007 QuickBird imagery
  • geomorphic zonation derived from 2007 QuickBird imagery

This data is offered using the Creative Commons Attribution license (CC BY 3.0 Unported), which “lets others distribute, remix, tweak, and build upon your work, even commercially, as long as they credit you for the original creation.”

The data from HyPhoon is available for the community to use in research projects, class assignments, algorithm development, application testing and validation, and in some cases also commercial applications. In other words, in the spirit of encouraging innovation, these datasets are offered as a community resource and open to your creativity.

We welcome your thoughts for new data you would like to see included, and also encourage you to contribute your own data or derived products to showcase on HyPhoon.

To access HyPhoon: http://hyphoon.hyspeedcomputing.com/

HyPhoon