In: Wagner W., Székely, B. (eds.): ISPRS TC VII Symposium - 100 Years ISPRS, Vienna, Austria, July 5-7, 2010, IAPRS, Vol. XXXVIII, Part 7B
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2003; Hay et al., 2003; Maxwell, 2005; Li et al., 2009; Smith
and Morton, 2010).
3. SUPERVISED DETERMINATION OF
SEGMENTATION PARAMETERS
3.1. Design of the Segmentation Tool
To address the issues existing in the trial-and-error selection of
segmentation parameters, a tool for supervised segmentation
parameter determination should meet the following
requirements (Maxwell, 2005):
a. Each execution of the tool is aimed at extracting one land
cover type and results in one level of the object
hierarchy;
b. Segmentation must be controlled and refined in an
iterative manner based on an object model;
c. The tool must rely on an initial segmentation as a start
state;
d. Scale, shape, and smoothness parameters must be
determined;
e. Parameter selection must be reproducible; and
f. The tool must demonstrate reasonably fast and efficient
performance.
The segmentation of an input image is performed on a number
of different levels to permit objects of different scales to be
extracted on their own level. By using this approach, objects
can be classified on the level where the segments are the most
meaningful and best represent the object of interest. This infers
that the user must have a specific land cover class in mind
when segmenting the image so that the parameters can be best
estimated and then refined through iteration. As a result, the
tool must aim to extract one particular land cover type each
time it is executed. By running the tool a number of times, a
hierarchy of object levels can then be developed.
3.2. Workflow of FbSP Optimizer
To meet the design requirements of the software tool, the
workflow for the supervised fuzzy-based determination of
segmentation parameters, i.e. the FbSP optimizer, was
developed as shown in Figure 3. To train the FbSP optimizer,
the input image needs to be initially segmented achieving an
over segmentation, i.e. the segments are smaller than the
objects of interest (see Figure 5.a). The small segments, also
called sub objects, can be selected to form a meaningful target
segment/object. The information of the target object and its sub
objects is then used to train the FbSP optimizer to determine
the optimal segmentation parameters for the target object
(Figure 4).
Figure 3. Workflow of the proposed FbSP optimizer. The values of the current Segmentation Parameters {Smoothness ( 1 -w compact ),
Shape (1-w) and Scale (s)), Sub objects information (Texture, Stability, Brightness, and Area) and Target Object information
(Texture, Stability, Brightness, Area, Rectangular Fit, and Compactness) are inputted into FbSP optimizer to train the FISs (Fuzzy
Inference Systems) to estimate the optimal Segmentation Parameters (1 -w compacl , 1-w, and 5) for the Target Object in an iterative
process.