Applications of Remotely Sensed TopoBathymetric Data

Presentations in the session will highlight mapping of the coastal and nearshore environment with satellite derived bathymetry, aerial topobathymetric lidar, and autonomous surface platforms.

Automatic Segmentation of Areas of Valid Bathymetry Retrieval from Satellite Imagery using Random Forest

The National Oceanic and Atmospheric Administration (NOAA) acquires nearshore bathymetric data to support safety of marine navigation, manage coastal ecosystems, and  model storm surge inundation. Vessel-based acoustic echosounding provides high-accuracy data, but  acquisition is inefficient and can be hazardous in very shallow areas. Satellite-derived bathymetry (SDB) provides a cost-effective alternative, and rapidly becoming increasingly more value, including through NOAA’s SatBathy software tool. However, a challenge with SDB is that it returns a value for every pixel in an input scene, generally with no indication of whether that value represents a valid bathymetric retrieval, an optically-deep area, cloud, boat, boat wake, or other obstruction. This study investigates using a random forest classifier with a range of surface and spectral features to automatically segment areas of valid bathymetry in SDB grids. The algorithm was trained on three sites and tested on four separate  geographically diverse sites, with test area predictions achieving up to 93% mean intersection over union accuracies. These methods can be used to rapidly assess SDB and are being adapted for operational use in NOAA’s SatBathy tool.

Matthew Sharr, NOAA National Geodetic Survey Remote Sensing Division

By Air, Sea and Space: A Multi-Sensor Approach for Alaska Coastal Topobathymetry Mapping

The task of surveying the Alaskan seafloor offers both an immense opportunity and a considerable challenge for all forms of hydrographic surveying. At the same time, coastal erosion and changing characteristics of the near-shore environment have accelerated in recent years, and the need for effective and efficient coastal surveying is ever-increasing. Given the extent of the Alaskan coastline, it is not feasible to map such a large region continuously with topobathymetric lidar, and TCarta has demonstrated the capabilities of Satellite Derived Bathymetry (SDB) and, more specifically, the integration of SDB datasets with existing mapping data to meet the Alaska Mapping Executive Committee (AMEC) goal of filling gaps in bathymetric data.

This presentation will address progress made in meeting the three priorities of the AMEC Alaska Coastal Mapping Strategy: (1) the acquisition of new bathymetric data processed using SDB techniques, validated by existing topobathymetric lidar and sonar-derived bathymetry datasets; (2) creation of a seamless topobathymetric DEM using SDB and existing sonar, lidar, etc datasets; and (3) provision of a workflow for combining datasets and an inventory of additional optimal SDB sites.

Exploiting the advantages of the modern era of earth imaging, the results of this project are designed to be immediately used to support Alaska coastal mapping priorities and data users.

Kyle Goodrich, TCarta

Satellite Derived Bathymetry (SDB) Using Physics-based Algorithm

Although active optical sensors (sonar and lidar) measure bathymetry with high accuracy and precision, the coverage is usually limited due to the high operational cost. Satellite imagery has a great advantage over the active sensors if high precision and accuracy of the satellite derived bathymetry (SDB) can be achieved. This research proposes a fully physics-based bathymetry algorithm by combining atmospheric and ocean optics. Top of the atmosphere reflectance from a satellite image over coastal zone must be corrected for the atmospheric contribution by handling Rayleigh scattering due to the atmospheric molecules and the aerosol attenuation, where aerosol optical depth, ozone, water vapor are used. Ocean optics theory forms a foundation for SDB and it consists of the water volume backscattering component and bottom reflected component. The bottom reflectance is modeled as a mixture of typical sand-like and grass-like bottom reflectance spectra. Thus, two bottom coefficients and the depth are three unknowns, and it is solved from nonlinear optimization. This physics-based approach does not require known depths if proper bottom spectra are used. With known depths, the accuracy and precision will be dramatically improved. Fast, low-cost, and vast areal bathymetry coverage using SDB is a powerful complementary technique to active sensors.  We demonstrate the accuracy and precision of SDB using various algorithms to optimize the estimated local bottom spectra.

Minsu Kim, KBR

High-Altitude Topographic and Bathymetric Lidar Sensor Test Results and Software

Woolpert aimed to address customer requirements for increased efficiency and flight safety in topo-bathy collections by collecting bathymetric data at 10,000 feet. To achieve this, the Woolpert team has been developing the Bathymetric Unmanned Littoral Lidar for Operational GEOINT (BULLDOG). BULLDOG is a multispectral, multichannel, topo-bathy lidar system designed to fly at higher altitudes and collect more data in less time than previous bathymetric systems. The patented lidar system utilizes three different wavelengths of light (532nm, 647nm, and 1064nm) distributed into five distinct channels optimized for shallow water, deep water, Raman, infrared, and Geiger-mode detectors. This innovative multispectral, multichannel lidar system employs green light for seafloor data collection, infrared light for topographic data collection and simultaneously captures high-resolution aerial images along coastlines. Additionally, by analyzing the Raman return, the system can differentiate between land and turbid water data. Woolpert is collaborating with various government agencies to implement and execute a field test plan for BULLDOG. This presentation will showcase the diverse geographic locations and environmental conditions in which data collection took place, including the capabilities of the post-processing software.

Nathan Hopper, Woolpert, Inc.

Force Multiplication Autonomy for Hydrographic Survey

The application of force multiplication principles in hydrographic surveying has become crucial for enhancing efficiency and productivity in challenging marine environments. This industry-focused presentation explores the successful utilization of Wave Adaptive Modular Vessels (WAM-V) during a large-scale hydrographic charting project in Nome, Alaska, conducted in collaboration with the NOAA Office of Coast Survey. The objective was to optimize survey operations and augment data acquisition capacity through the strategic deployment of autonomous WAM-Vs.

The presentation will highlight the practical implementation of force multiplication strategies using WAM-Vs, demonstrating their adaptability and efficacy in the field. The coastal region of Nome, Alaska, known for its harsh conditions, served as an ideal testbed for this industry-driven initiative. By leveraging the autonomous capabilities of WAM-Vs, the project team was able to overcome operational challenges associated with shallow waters, unpredictable weather patterns, and other environmental obstacles.

The presentation will delve into the technical aspects of integrating autonomy within the WAM-Vs, enabling predefined mission execution, autonomous data collection, and seamless collaboration between multiple vessels and the benefits of this approach. The utilization of WAM-Vs as force multipliers allowed for simultaneous data acquisition from multiple locations, significantly increasing the surveying capacity.

Dave Neff, Woolpert, Inc.

Synchronization of Airborne Lidar and Bathymetry Surveying for Coastal Mapping

Airborne bathymetry is a relatively new surveying approach which allows to investigate waters and deliver topo bathymetric maps where traditional methods with boats or USV boats are forbidden or hardly applicable due to ecological reasons or complex terrain. One of the key advantages of the method is the ability to use the same drone hardware for multiple types of studies: photogrammetry, LiDAR, bathymetry.  A small team of 1-3 surveyors could perform large scale aerial studies without additional paper bureaucracy associated with boat route & petrol spent approvals. The accuracy of data collected with a UAV is comparable with the quality of data collected with traditional boat methods. UAV-based bathymetry can be considered as a game changer for reservoir characterization and modeling, environmental monitoring, studies of sea, lake or riverbeds. TOPODRONE will present an exclusive case study from Italy. The team has collected and synchronised LiDAR and bathymetry data being challenged with the wave height as of 1m.

Alexander Lopukhov, TOPODRONE