The quick bird high resolution remote sensing image of
Shenyang which is obtained in September, 2006 is used as the
research data(see Figure l),In this paper, the software ENVI and
Matlab Basic Mentality is used. First, we make a pre-treatment
to the remote sensing image; Second we use the supervised
classification method- Support Vector Machine to classify the
remote sensing image, convert the classified image into binary
image; then we use the mathematics morphology method to
simplify the image data, maintain their basic shape
characteristics, and except the irrelevant structure characteristic,
the tiny branch and the noise, extract the road skeleton; at last
we use the seed growing algorithm method to extract the road
median line of certain length and direction, and overlay it with
the original image to assess precision
2.2 Image Clustering Segmentation based on Support
Vector Machine
The Support Vector Machine classification (Support Vector
Machine is SVM) is one kind of machine learning method that
is establishment in the foundation of the statistical study
theory(Statistical Learning Theory or SLT) , with the aid of the
optimization method to solve machine learning question, its
main thought aims at two classification questions, seeks a
optimization classification in the hyper plane which is token
as the classified plane to guarantee the smallest classification
error [ 18 \ This method suits the limited sample (small sample)
question, has solved the problems existing in the traditional
method(such as neural net) in the great degree , like model
choice, study on-linearity, multi-dimensional question, partial
minimum point question and so on. The biggest different
between the Support Vector Machine(SVM) and the traditional
statistical pattem is that the Support Vector Machine cannot
cause the Hughes phenomenon (Hughes phenomenon) - to the
limited training sample along with the characteristic
dimension increases the classification precision reduces, and
when two categories spectrum average values extremely
approach, SVM also can separate these two categories
according to these limited samples .But for remote sensing
image ,characteristic dimension generally is many, moreover
the category spectrum is quite close in the panchromatic image.
Appling SVM to remote sensing image of the multi- spectral,
the high spectrum or the high spatial resolution can obtain good
effect, also can enhance the remote sensing image classification
precision. This classified method is insensitive to the noise,
increases the classification precision, suits the non-linear
classification, the classification result is neat, suits GIS,
extremely suits to four wave bands high resolution data. The
following(see Figure 2) is the classification result
2.
Figure 1 The original image
EXPERIMENTAL RESEARCH OF ROAD
EXTRACTION
This method mainly includes the following several steps: The
image pretreatment; use the Support Vector Machine
segmentation method to obtain binary image; process the binary
image by mathematics morphology method, obtain the skeleton
image; through limiting the length and the direction to reject the
tiny branch using seed growth to obtain the final road median
line; finally superpose the road median line with the original
image to assess precision.
2.1 Image Pretreating
The mainly work of the Image pretreatment is image
enhancement, deleting cloud and mist noise, the aim is to wipe
off irrelevance noise, enhance image quality, stand out the
need information ,which is advantageous to interpretation and
further processes, there are many image enhancement methods,
such as spatial filter, color transform ,image operation, multi
spectrum change and so on .But the concrete method must meet
the concrete experiment image data need, the image in this
paper hasn’t cloud and mist, is carried on color transform,
according to the experiment.
Figure 2 The result of Support Vector Machine Classification
Stochastically selects 30 ground control points to carry on the
precision analysis, the reference [19] thought that the extracting
result quality has very big relation with the initial clustering,
whether clustering precise is high or not plays a important role
to the road. This method classification overall precision
achieves 88.406%, the kappa coefficient is 84.4%.(see Figure3).