『Abstract
In order to develop quantitative seafloor sediment classification
techniques it is important to acknowledge that by nature the boundaries
between soft sediments are characterized by transition zones and
therefore are indeterminate and gradual. A fuzzy clustering method,
fuzzy c-means (FCM), was used to identify these transition zones
within a subset of the data used to generate the Australian Seascapes
classification model. The overlapping classes and gradual boundaries
resulting from the fuzzy c-means algorithm provided estimates
of sediment boundaries that are a closer model of reality than
sharp boundaries. FCM output is given in the form of membership
layers for each class, hard classes for each grid cell based on
the maximum membership value, and a confusion index layer quantifying
uncertainty in class attribution. The confusion index layer provided
a spatial representation of transition zones and overlap between
seafloor classes and highlighted areas if greatest uncertainty.
We extended the standard FCM algorithm by applying the new FMLE
fuzzy clustering algorithm that takes into account spatial relationships
in the data. In addition, we implemented and applied new cluster
validity techniques, PCAES, PBMF, and XB to determine the optimal
number of clusters in the data, which is a novel pattern recognition
application for seabed mapping. The 5-class FCM classification
provided the most reliable result. The results of this research
were tested and validated on a simulated dataset and then the
clustering and validation algorithms were applied to marine sediment
data to identify Seascapes. The new results were compared with
previously published Seascapes classes identified with hard ISODATA
clustering techniques from GeoScience Australia's Seascapes classification
result. With the increasing use of physical surrogates to explain
marine biodiversity, this research plays a crucial role in the
development of techniques to identify habitat zones on the seabed.
Keywords: marine mapping; fuzzy boundaries; fuzzy c-means (FCM)
clustering; cluster validity; uncertainty analysis』
1. Introduction
2. Methods
2.1. Study area and data set
2.2. Fuzzy c-means (FCM) classification
2.3. Fuzzy maximum likelihood estimation (FMLE) clustering
2.4. Spatial clustering
2.5. Cluster validation methods
2.6. Confusion in geographic boundary identification
2.7. Simulation
3. Results
3.1. Fuzzy c-means (FCM) Seascapes classification
4. Discussion
5. Conclusions
Acknowledgements
References