icesat2-bathymetry / information

Information and resources about bathymetric data from NASA's ICESat-2 mission, created by the ICESat-2 Science Team Bathymetry Working Group.

ICESat-2 Bathymetry Overview

Interested in using ICESat-2 bathymetry data or exploring current research? This repository contains information about current and past research collected by members of the ICESat-2 bathymetry working group.

What can ICESat-2 do?

The ICESat-2 mission is a satellite laser altimeter launched in 2018. Its photon counting lidar makes precise elevation measurements globally, including at high-latitudes. In addition to significant contributions to glaciology and forest mapping, ICESat-2 has proven capable of measuring the depth of the seafloor with sub-meter accuracy, and as deep as 40m in good conditions.

What's the best way to access ICESat-2 data?

The working group is currently in the process of creating a bathymetric data product. Until then, users should download the geolocated photon data product ATL03 which contains all photon data. We recommend downloading ICESat-2 geolocated photon data either using web based tools like NSIDC and OpenAltimetry, or programmatically with tools like SlideRule and IcePyx.

For bathymetry focused data downloading tutorials, check out one of the demo notebooks here or here.

The Science Team also maintains a list of general ICESat-2 tools and services available here.

How do I correct depth data for refraction?

Refraction-corrected depths are not currently calculated for existing data, although this will likely be included on a future bathymetric product. The approach outlined in Parrish, Magruder et al. 2019 has been frequently used and validated in research, although new approaches have been explored in the literature as well.

Code implementations of Parrish 2019 are available in Python and MATLAB.

The angle of refraction, $\phi$, in the above figure is calculated from Snell's law and requires having a value for $n_2$, which can be computed as described in the discussion of the refractive index of seawater and freshwater.

A water surface model (WSM) is also needed, and obtaining a WSM can be one of the more challenging aspects of refraction correction.

How do I extract the water surface and seafloor returns?

Photon data can be labeled by hand using the OpenOceans Manual Classification Tool or PhotonLabeler tools.

Automated methods of labeling large amounts of data are an open area of research. Which method is best may depend on your use case and desired accuracy.

Automated Seafloor Extraction Codes

1. C-SHELPh

• Automated retrieval of bathy photons and ML regression modeling for satellite derived bathymetry. Link to code. Link to Publication.

2. More coming soon.

ICESat-2 Bathymetry Member Research

Nearshore bathymetry and seafloor property studies from Space lidars: CALIPSO and ICESat-2, Xiaomei Lu, Yongxiang Hu, Ali Omar, Yuekui Yang, Mark Vaughan, Sharon Rodier, Anne Garnier, Robert Ryan, Brian Getzewich, and Charles Trepte. (2022)

A purely spaceborne open source approach for regional bathymetry mapping Nathan Thomas; Brian Lee; Oliver Coutts; Pete Bunting; David Lagomasino; Lola Fatoyinbo (2022)

Diffuse Attenuation Coefficient (Kd) from ICESat-2 ATLAS Spaceborne Lidar Using Random-Forest Regression Corcoran, Forrest; Parrish, Christopher. (2021) Link to code.

Recent Datasets by Members

Bahamas Median DEM, from A PURELY SPACEBORNE OPEN SOURCE APPROACH FOR REGIONAL BATHYMETRY MAPPING (2022).

• A median composite DEM derived from a fusion of ICESat-2 and Landsat-8 data, created with a Extra Trees Regressor. Units are in m depth.

Other Useful Data and Tools

• NOAA Digital Coast - Repository for NOAA survey data. In particular, elevation data and topobathymetric lidar surveys available here have been useful for validation of ICESat-2 depth data.
• NOAA Bathymetric Data Viewer - Great repository for ship-based sounding data.
• General Bathymetric Chart of the Oceans (GEBCO) - Global ocean bathymetric data available to download as a gridded product. -EMODnet Bathymetry - European Marine Observation and Data Network (EMODnet) bathymetry portal provides a service for viewing and downloading a harmonised Digital Terrain Model (DTM) for the European sea regions.
• SeaBASS - Archived data include measurements of apparent and inherent optical properties, phytoplankton pigment concentrations, and other related oceanographic and atmospheric data, such as water temperature, salinity, stimulated fluorescence, and aerosol optical thickness.
• Tides and water levels - Various official tidal predictions, datums, and more provided by NOAA.
• Turbidity and ocean color - The ocean color science team in the Center for Satellite Applications and Research (STAR) of NOAA/NESDIS seeks to develop improved ocean color products from the current and future ocean color satellite sensors including SeaWIFS, MODIS, VIIRS, SNPP, JPSS, and many more.
• Vertical datum transformations - VDatum is a free software tool designed to vertically transform geospatial data among a variety of tidal, orthometric and ellipsoidal vertical datums.
• Sentinel-2/Copernicus Open Access - Source for downloading imagery from the Sentinel-2 satellite, as well as other sentinel products.
• MODIS-1B data - Calibrated and geolocated at-aperture radiances for 36 bands generated from MODIS Level 1A sensor counts (MOD 01).
• GDAL - GDAL is a translator library for raster and vector geospatial data formats.
• PSMSL - Permanent Service for Mean Sea Level (PSMSL) stations with GNSS ellipsoid heights.
• ShallowBathymetryEverywhere - Examples of ICESat-2-aided SDB for select locations around the world.
• Various geospatial python libraries such as pyproj, geopandas, rasterio, shapely, etc...

Publications

The working group also maintains a shared Zotero library of ICESat-2 bathymetry related publications. You can access it here.

Contributing Working Group Members

Jonathan Markel
PhD Student, The University of Texas at Austin
[email protected]

Dr. Chris Parrish
Professor, Oregon State University
[email protected]

Dr. Nathan Thomas
Assistant Research Scientist, NASA Goddard
[email protected]

Kim Lowell
Research Scientist, Centre for Coastal and Ocean Mapping
[email protected]

Dr. Xiomei Lu
Research Scientist, SSAI/NASA Langley Research Center
[email protected]