Applications of Remotely Sensed TopoBathymetric Data – II

Presentations in the session will highlight acquisition, processing, and workflows for mapping of the coastal and nearshore environment with satellite derived bathymetry, aerial topobathymetric lidar, SAR, and other sensors.

2:00 PM – 2:15 PM – Benefits of the Wide-Footprint Green & Narrow NIR Lasers of a Topo-Bathymetric Lidar for Terrain Mapping

Traditional mapping on land has been carried out using NIR lasers on topographic lidar sensors. These lasers typically have a small beam divergence resulting in a narrow beam for penetration of the forest canopy through gaps and precise ground detection. However, in dense canopy, for example conifer forest or dense shrubs & grasses. In these cases, the NIR laser potentially provides no ground return, or a vegetation biased return that is often mistakenly classified as a ground return.  We have utilized the Leica Chirotera topo-bathymetric lidar sensor for topographic surveys and have observed some benefits of the green laser (515 nm) with a 4 mrad beam divergence to compliment and in some cases supplement the NIR laser returns (1064 nm) with a 0.5 mrad. In addition to the green lasers ability to penetrate the vegetation deeper, it is also very good at picking up returns from thin wires like power distribution and telecommunication lines. The disadvantage of the larger footprint of the green laser is a higher uncertainty in the precision of the elevation of the ground return for undulating and hummocky terrain within the footprint.

Tim Webster, Applied Geomatics Research Group, Nova Scotia Community College

2:15 PM – 2:30 PM – Between the Banks: Advancing Riverine Bathymetric Mapping with the Helicopter-Based BLAST System

Mapping riverine environments using airborne lidar presents persistent challenges due to rugged terrain, variable water clarity, and the difficulty of maintaining low-altitude, channel-following flight paths with fixed-wing platforms. To address these limitations, we developed BLAST (Bathymetric Lidar And Sensor Technology) System V2, a modular, helicopter-based system designed specifically for complex inland waterway mapping. This second-generation system integrates the RIEGL VQ-860-G bathymetric lidar and VUX-240 near-infrared sensor into a single nose-mounted pod compatible with the Bell Long Ranger airframe.

This platform enables stable, low-altitude data acquisition along sinuous and topographically constrained river corridors, expanding the spatial reach of airborne bathymetric surveys into areas traditionally underserved by fixed-wing systems. We will present system design considerations, data collection protocols, and sensor integration strategies, along with results from recent deployments across varied hydrological environments with our first-generation system.

Case studies include support for flood modeling, aquatic habitat assessments, and post-disaster terrain analysis, with discussion of data quality metrics, spatial resolution, water penetration performance, and operational efficiency. We will also describe lessons learned in optimizing flight planning, data extraction, sensor alignment, and calibration under dynamic terrain conditions.

BLAST V2 demonstrates how targeted platform and sensor integration can improve access to high-resolution bathymetric data in complex fluvial systems, offering a practical alternative to both traditional airborne and in-situ methods.

Andres Vargas, NV5

2:30 PM – 2:45 PM – Advantages and Challenges of Mapping Riverine Environments with Aerial Topobathymetric Lidar

Aerial topobathymetric lidar is an advanced remote sensing technology that integrates topographic and bathymetric lidar to collect high-resolution elevation data of both terrestrial and submerged environments. This technique enables efficient, accurate mapping of coastlines, river channels, floodplains, and adjacent landscapes, providing critical data for hydrologic modeling, habitat assessment, and resource management. Traditionally, topobathymetric lidar has largely been used for coastal mapping, and is now being used more and more for mapping riverine environments.

This presentation will highlight the use of aerial topobathymetric lidar through several riverine focused projects completed for various federal, state, and local agencies. Looking through the lens of specific projects, this presentation will focus on three key factors. The first being the primary differences between coastal and riverine aerial topobathymetric lidar mapping. The second being a deeper dive into the specific challenges of mapping riverine environments with aerial topobathymetric lidar, such as acquisition planning, bathymetric composition dynamics, and refraction challenges as they relate to water clarity and water detection. The third being the value and advantages of this technology in supporting integrated watershed management, flood risk assessment, and environmental monitoring.

Jackson McGraw, Dewberry

2:45 PM – 3:00 PM – USGS National Seamless 1-Meter DEM for Elevation Derived Hydrography Process Overview and Lessons Learned

The National Geospatial Technical Operations Center and the Earth Resources Observation and Science Center of the U.S. Geological Survey researched and created a new National Seamless 1-m (S1M) Digital Elevation Model (DEM) to support the 3D Hydrography Program. The S1M debuted in April of 2025 and is expected to cover half of the conterminous United States by 2028. A seamless 1-m DEM requires merging multiple lidar projects with unique lidar sensors, bare-earth DEM generation methodologies, source resolution, datums/projections, geoids (mean sea level model), unit of measure, and NoData values. We chose the North American Datum of 1983 USA Contiguous Albers Equal Area Conic projection for this dataset due to the size of watersheds and the fact they do not respect political or UTM boundaries. We updated the vertical datum, North American Vertical Datum of 1988, to the current GEOID18 model. Our workflow consists of data selection and staging, source transformation, processing, spatial and XML metadata creation, vertical accuracy assessment, and publication. Under processing, we developed methodologies for void detection, small and large void backfilling, and blending. Specifically, we have blending between lidar-to-lidar projects, and lidar-to-coarser datasets such as the 1/9 and 1/3 arc-second seamless DEMs in areas where we did not have 3D Elevation Program lidar or had restricted areas such as military bases or tribal lands. Seamlines are placed optimally using difference rasters between projects to detect significant offsets and temporal changes. This presentation will also show the current status of coverage and where to find and download the S1M DEMs in ScienceBase (https://doi.org/10.5066/P13LJKFS) and The National Map (https://apps.nationalmap.gov/downloader/). Finally, we will cover some of the lessons we learned in delivering a groundbreaking new product to the Nation.

Barry Miller, U.S. Geological Survey

3:00 PM – 3:15 PM – Leica CoastalMapper – Experiences From Operations

At GeoWeek 2025, Leica Geosystems unveiled the revolutionary Leica CoastalMapper, a bathymetric LiDAR sensor boasting up to a 250% increase in data collection efficiency. This presentation will delve into our operational experiences with this cutting-edge sensor.

We will explore the following key topics:

• Depth Penetration: How does the Leica CoastalMapper’s depth penetration, measured against diffuse attenuation (KdxDmax), compare to previous models like Chiroptera and HawkEye? We’ll examine the impact of survey altitude, system settings and local seabed reflectance.
• Hydrographic Object Detection: What sizes of hydrographic objects can the CoastalMapper detect on the seabed? We’ll discuss the influence of system settings and survey parameters, and whether we can establish a Hydrographic Order Detection capability that meets international standards.
• Shallow Water Performance: Essential for river surveys and areas where the land-water interface is critical, we’ll assess the system’s performance and the benefits of the super-shallow channel.
• Turbid Water Performance: In the often turbid waters of coastal and riverine environments, how does the CoastalMapper perform? We’ll compare the effectiveness of turbid water algorithms versus standard peak detection algorithms.
• Confidence of Bathymetric Returns: The confidence level of bathymetric returns varies, with stronger returns at average depths being more reliable than those near depth extinction. We’ll explore how to measure and use confidence to filter valid returns from noise.
• Active Green/NIR Blending: The CoastalMapper features co-aligned NIR returns for all green returns above water, enabling an active NDVI-like property. We’ll discuss the potential new applications this feature brings to bathy LiDAR.
• Topographic and Imaging Performance: Incorporating the latest topographic and imaging technology, we’ll highlight how these capabilities enhance bathymetry use cases and maximize sensor investment returns.
• Ease of operation: Bathy LiDAR is not just about the sensor it is also about the people and infrastructure. We’ll hi-lite what improvements we made to the ease of operation of the sensor and the data processing workflow.

With the Leica CoastalMapper, we aim to revolutionize large-scale bathymetric LiDAR data collection, enabling cost-effective statewide and countrywide coastal and inland mapping projects. Comprehensive digital elevation models spanning the land-water boundary are crucial for applications such as infrastructure investments in coastal zones, flood protection, coastal erosion mitigation, shallow area sea charts and environmental investigations.

Anders Ekelund, Hexagon

3:15 PM – 3:30 PM – From the Air and Under the Water: Integrating UAS Lidar and Traditional Bathymetric Data for Reservoir Management

The presentation outlines an integrated workflow that combines aerial LiDAR data with bathymetric measurements to produce high-accuracy topobathymetric models. Using a unified processing environment in LP360, the method streamlines point-cloud generation, classification, bathymetry merging, and quality control into a single workflow. The approach enhances efficiency, reduces processing steps, and ensures consistent results for applications such as reservoir monitoring, hydroelectric management, and environmental analysis. Case studies demonstrate how this integrated technique improves surface modeling, supports precise elevation–area–volume updates, and delivers reliable datasets for engineering and water-resource decision-making.

Thadeu Lugarini, GeoCue Group