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International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Vol XXXV, Part B2. Istanbul 2004
classes. But such approach does not take into account features
of spatial interaction of classes on thematic map (Verburg P.H.
et al., 2003).
In the paper the approach, with combined application of
original algorithm of RS images interpretation, geoinformation
system (GIS) and also algorithm of enhanced designing of
forecast maps is developing. The features of the proposed
algorithms are considered and investigation results of these
algorithms using modeled aerospace images and real TS RS
images are discussed.
2. PROCESS DESCRIPTION
Processing and interpretation of TS RS images using the
proposed methods and approaches are based upon two
sequential stages. In the first stage TS RS images are classified
by the original advanced interpretation algorithm with separate
processing of spectral and spatial features of RS images. It
allows to obtain the less noisiness final thematic map and to
increase its classification accuracy compared to traditional
interpretation, RS and mapping software. The first stage of RS
images interpretation is a key stage, because on the basis of
interpretation results the forecast maps will be designed. In that
case more accurate and adequate of interpretation results will
lead to more accurate and adequate forecast results.
In the second stage the obtained raster thematic maps are
processed by the original TS analysis algorithm, which is based
upon Markov chains and CA processing algorithm, includes the
optimal neighborhood size determination. This TS analysis
algorithm allows to consider not only the probability of
transition one class to the another, but the spatial interclass
correlation.
Let's consider the algorithm applied in the stages of the
advanced interpretation and the algorithm of the enhanced TS
analysis in details.
2.1 First stage — advanced interpretation
Advanced interpretation in the framework of the proposed
approaches is based upon Bayes decision rule of empirical risk
minimization:
p(o,)p(X |œ,) ‘ (1)
pio xy M :
S p(œ,)p(X | œ, )
where p(o,) — prior probability of class i, M — the number of
classes, pO 1o.) - conditional probability density of class i.
At the same time according to (1) interpretation in two steps is
performed. In the first step the posterior probability maps for
each classes are designed, at that the feature space is
considering spatial characteristics. In the second stage
according to (1) designed maps are to be used as prior
probabilities of classes and the feature space consist only of
Spectral features.
Besides, it should be noted that in the first step cither statistical
or artificial neural network (ANN) classification could be used.
493
Statistical classification is based upon combined application of
parametric and nonparametric algorithm of density estimation
depends on the agreement of the data with the normal
distribution according to the chi-square criterion, and also
statistical classification includes standard parallelepiped
classification algorithm. The simple and fast parallelepiped
classification algorithm is applied in case the sample data range
is not intersected by data range of any other samples.
ANN classification is implemented together with the approach
to the storage and the search of the ANNs in a database. The
general purpose of the approach is to make the process of
ANNs topology and parameters definition easier and also to
make the learning process of ANN faster. The search might be
done with test of sign-rank correlation between the investigated
data sample and the ANN train data sample stored in the
database. The possibility of ANN search makes the ANN
learning more predictable and robust. That is why in case of
successful search of the appropriate stored ANN for
investigated data sample the designing of prior probability
maps is performed by ANN classification.
2.2 Second stage — forecast maps designing
TS thematic maps, designed in the first stage, and other
additional data, obtained by including GIS are carried out by
enhanced TS analysis algorithm. The algorithm includes
iterative performing of three operations.
The first operation of the considering process is the analysis of
the neighborhood characteristics of the raster interpreted
thematic maps. At that the optimal scale of classes
representation is being determined. The optimal scale needs
further for the effective CA application.
The second operation is the constructing of transition matrix
(TM). The operation includes the analysis of two and more
thematic maps using first-order or high-order Markov chains
respectively. The use of suitability maps, which show the
probability of change one class to another, allows to range all
image elements from high disposed to change till low disposed
to change.
The final operation is processing of primary forecast map by
CA with the optimal neighborhood size, defined in the first
tep.
N
The final result of the enhanced TS analysis algorithm is a
forecast map for the further time step. To perform longer
forecast it is needed to pass the obtained forecast map to the
input of the algorithm as the TS input thematic map.
3. FEATURES OF APPLIED ALGORITHMS
One of the original algorithms applied for interpretation of RS
images is the density estimation. nonparametric algorithm,
which is based upon Rosenblatt-Parzen (RP) algorithm and k-
nearest neighbour (k-NN) algorithm. The original algorithm
provides a computational cost over dozens times compared to
existing nonparametric algorithms. Moreover the ways of
forming feature space for both statistical and neural network
approaches are original. Also the approach to processing of
thematic maps by CA with optimal neighbourhood size defined
by the enrichment factor is original. It is proposed to consider
these features more detailed.