15-1 Comparing Phase Measuring Side-Scan Sonar and Multibeam Bathymetry in Shallow Coastal Waters

Session: Integrated Digital Workflows in Geoscience: Mapping, Marine Exploration, and Machine Learning

Presenting Author:

Authors:

Abstract:

Bathymetric surveys in shallow waters are essential for navigation safety and coastal management but can be prohibitive due to cost, time, and survey efficiency. This study compares bathymetric products from a phase measuring side-scan sonar (PMSS) survey conducted in fall 2025 by the Center for Coastal Studies (CCS) in Provincetown Harbor, Massachusetts, with multibeam echosounder (MBES) data collected by NOAA in fall 2023 to support nautical chart updates.

The PMSS survey used an EdgeTech 6205-S2 operating at 550 kHz for both bathymetry and side-scan imagery, and a second, higher-resolution side-scan imagery frequency (850 kHz). NOAA used a dual-head Kongsberg Maritime EM 2040C multibeam echosounder operating in the 200–400 kHz frequency range. Positioning, attitude, and sound velocity measurements were collected with comparable instruments, enabling a direct dataset comparison.

In deeper areas of the harbor (>5 m), MBES line spacing was ~15 m. In shallow regions (3.5 to 5m) line spacing was 8 m. For all PMSS surveys line spacing was ~40 m resulting in comparable bottom coverage. PMSS surveys were also collected in very shallower areas, ~1.5 m, using 20 m line spacing. Bathymetric surfaces from PMSS and MBES show excellent agreement, with mean difference of 0.02 m, and a standard deviation of 0.06 m across overlapping survey areas. This accuracy results from the combination of data acquisition and post-processing techniques

PMSS also provides co-located side-scan, offering higher-resolution seafloor characterization than MBES backscatter, particularly for targets smaller than twice the bathymetric cell grid. While multibeam echosounders are commonly used as the standard for high-accuracy hydrographic surveys, these results suggest that PMSS can achieve comparable bathymetric results while improving survey efficiency. It represents a meaningful enhancement to seafloor mapping approaches, especially where shallow water operational constraints are critical.

Geological Society of America Abstracts with Programs. Vol. 58, No. 2, 2026

© Copyright 2026 The Geological Society of America (GSA), all rights reserved.