This session explores emerging approaches to mapping rivers, coastlines, and shallow-water environments through the integration of topo-bathymetric lidar, multibeam sonar, and hydrographic survey workflows. Presentations highlight advances in data acquisition, feature detection, navigation safety applications, and flood hazard mapping while examining the opportunities and limitations of modern hydrographic technologies.
12:30 PM – 12:45 PM
Mapping Dynamic River Systems: Integrating Multibeam Sonar and Topo-Bathymetric Lidar for Comprehensive Hydrospatial Surveys
Presented by Dave Bernstein, NV5
Modern riverine topo-bathymetric surveys provide critical datasets that support flood modeling, watershed management, infrastructure planning, habitat assessment, and long-term geomorphic monitoring. As demand grows for high-resolution elevation data across riverine environments, hydrographic surveys must overcome unique operational challenges not typically encountered in coastal or offshore applications.
This presentation highlights recent multibeam echosounder (MBES) and topo-bathymetric lidar surveys conducted on large river systems for Federal and State agencies that support a range of stakeholders. Although the projects support different program objectives, both demonstrate how full-coverage bathymetric mapping contributes to a broader understanding of river systems through the integration of submerged channel morphology with terrestrial topographic datasets such as lidar.
This effort highlights critical project planning and field execution strategies, including survey platform selection, equipment mobilization, and adaptive acquisition techniques required to operate safely and efficiently in dynamic river environments characterized by shallow water, rapidly changing channel conditions, strong currents, submerged hazards, and limited access.
Challenges from these projects illustrate the importance of combining experienced field crews, efficient survey systems, and adaptive workflows merging mapping technologies to produce high-quality bathymetric datasets that support a wide range of scientific, engineering, and resource management applications. Attendees will gain insight into both the technical and logistical considerations associated with executing large-scale riverine hydrospatial surveys using sonar and topo-bathymetric lidar, and the value these datasets provide to federal and state stakeholders
12:45 PM – 1:00 PM
Topo-Bathymetric Lidar Mapping of the Coast of New Brunswick to Support Coastal Flood Hazard Mapping
Presented by Tim Webster, Nova Scotia Community College
In the fall of 2025 Hexagon began a project with the New Brunswick government to map a large section of the Northumberland Strait coast in NB from the Confederation Bridge to Buctouche. Two Leica Chiroptera 4X (CH4X) systems were deployed along with two boat teams charged with doing water clarity measurements to ensure the maximum depth penetration possible from the lidar sensors. The NSCC CH4X system was assigned the southern set of blocks from the bridge to Cocagne. The NB government outlined an outer limit off the coast which represented the desired coverage of bathymetry of the intertidal and subtidal zone to be acquired. Results from the surveys indicate that all areas were completed and the depth requirement was met or exceeded for all study sites. The NSCC also deployed a water clarity information system (WCIS) to establish typical baseline water clarity conditions within the coastal areas. This included two turbidity sensors with cellular modems to allow real-time access to the water clarity as well conducted coastal surveys checking on Secchi depths and recording conditions. Flights were based out of the Moncton airport and the entire mission took just over 1 month. Deliverables included both the classified lidar point cloud and digital elevation models. The data are planned to be utilized to enhance understanding of intertidal zones in relation to coastal flood hazard mapping in New Brunswick. Additional data related to seabed roughness and vegetation could be extracted from the data that may aid in refining model outputs to improve validation of the models. This presentation will describe the planning, logistics and execution of the surveys along with data processing and examples of outputs from the survey.
1:00 PM – 1:15 PM
Bathymetric Lidar Hydrographic Objects Detection Capability
Presented by Anders Ekelund, Hexagon
Although airborne bathymetric lidar has been operational for more than five decades, some hydrographic offices remain cautious about adopting the technology for hydrographic charting applications. This caution is understandable, but it also limits the use of a highly efficient survey method for large shallow-water areas, particularly where vessel-based multibeam echo sounding is less cost-effective.
A key reason for this hesitation is uncertainty regarding the ability of airborne bathymetric lidar systems to detect hydrographic objects that meet the requirements of IHO S-44 Order 1A, represented by a 2 × 2 × 2 m object, and Special Order, represented by a 1 × 1 × 1 m object.
Because of the design constraints of airborne bathymetric lidar systems, laser eye-safety requirements, and, in particular, the broadening of the laser beam caused by scattering within the water column, hydrographic objects—especially those corresponding to Special Order dimensions—are often significantly smaller than the laser footprint on the seabed. Near the system’s maximum depth penetration, a detectable return generally requires sufficient reflection from a substantial portion of the laser footprint. Consequently, when the projected area of a hydrographic object is small relative to the footprint, object returns may no longer be distinguishable at that depth. This limitation is not resolved by increasing point density alone; beyond a certain depth, returns from small objects are lost regardless of the sampling density.
Does this mean that airborne bathymetric lidar is unsuitable for hydrographic charting? Not at all! Airborne bathymetric lidar sensors can provide strong hydrographic object-detection performance in shallow-water environments. When the depth-dependent limitations of object detection are properly understood and accounted for, the resulting data can provide valuable and operationally relevant input for charting applications.
This presentation will provide a theoretical framework for assessing the hydrographic object-detection capability of airborne bathymetric lidar systems. It will present results from practical evaluations of the Leica CoastalMapper and Leica Chiroptera-5 systems, benchmarked against multibeam reference data containing numerous charted hydrographic objects. Tests conducted at different flying altitudes will be discussed to illustrate the influence of acquisition geometry on object detection. The presentation will also introduce the Leica confidence value of the return, provided as an extra byte in the LAS data format, and discuss its relevance for data interpretation. The objective is to provide the audience with a scientifically grounded understanding of the extent to which these systems can support IHO S-44 Order 1A and Special Order charting applications.
1:15 PM – 1:30 PM
Identifying Navigationally Significant Features in Bathymetric Lidar
Presented by Karen Hart, Woolpert
Topo‑bathymetric lidar supports the development and maintenance of hydrographic products for navigation. On recent projects, Woolpert acquired bathymetric data consistent with the International Hydrogrpahic Office (IHO) Standards for Hydrographic Surveys S-44 Order 1a, supporting detection of seafloor features as small as 2 × 2 meters in water depths to 20 meters. The point density was adequate for feature detection; however, total propagated uncertainty (TPU) calculated in cBLUE did not consistently meet IHO Order 1a beyond 20 meters depth. Additional flight lines were collected to increase coverage and point density, but additional data density does not improve TPU results. Even so, the data revealed navigationally important seafloor features, including previously uncharted shallow-water obstructions, allowing customers to enhance shallow-water safety-of-navigation products. These outcomes demonstrate that topo‑bathymetric lidar can support electronic navigational chart (ENC) updates, even when all hydrographic specification requirements are not fully met.
