Work

Comparing pixel-and object-based approaches for classifying benthic habitats

Year: 2025

Type: article

Abstract: Benthic habitat mapping is essential for effective marine spatial planning, yet choosing appropriate classification methods remains challenging. This study compares pixel-based (PB) and object-based image analysis (OBIA) approaches within a hierarchical random forest framework to classify benthic biotopes in Apollo Marine Park and along the Cape Otway coastline, Victoria, Australia. High-resolution multibeam echosounder (MBES)-derived bathymetry and backscatter data were used, with backscatter harmonised across systems via a bulk shift method. The Supercells segmentation technique supported OBIA-based classifications. We assessed performance across three hierarchical biotope levels (BC2–BC4) using accuracy, F1 scores, and prediction certainty. Both PB and OBIA approaches showed strong classification performance with no statistically significant differences in accuracy (all p > 0.14). OBIA models achieved higher F1-scores at the intermediate classification level (BC3: F1 = 0.88) compared to PB (F1 = 0.82), whereas PB outperformed OBIA at the coarsest level (BC2: PB F1 = 0.86 vs. OBIA F1 = 0.79) and at the most detailed level (BC4: PB F1 = 0.73 vs. OBIA F1 = 0.68). Accuracy differences across levels were minimal (1–1.5 %). Spatially, both approaches identified consistent biotope patterns, but differed in map texture: PB models captured fine-scale detail with noticeable fragmentation, while OBIA maps were more generalised and spatially coherent. Certainty maps indicated comparable model confidence. These results highlight the need to balance spatial detail with interpretability when selecting classification methods. In contexts with complex seafloor structure and class imbalance, aligning the classification approach with the intended map use is critical for supporting marine spatial planning stakeholders, including conservation managers, policymakers, and environmental consultants, in making informed decisions.

Source: Estuarine Coastal and Shelf Science

DOI: 10.1016/j.ecss.2025.109601

Authors: Henry O.J. Simmons, Oli Dalby, Daniel Ierodiaconou, Mary A. Young

Language: English

Topic: Underwater Acoustics Research

Subfield: Oceanography

Field: Earth and Planetary Sciences

Domain: Physical Sciences

SDG: Life below water

Open Access status: hybrid

Estimated APC paid: $3,410

Funders: Parks Victoria, Deakin University, Department of Energy, Environment and Climate Action