بهبود طبقه بندی طیفی- مکانی جنگل پوشای مینیمم با کاهش ابعاد تصاویر فراطیفی

فن آوری سنجش از دور فراطیفی دارای کاربردهای فراوان در طبقه بندی پوشش های زمین و بررسی تغییرات آنها است. با پیشرفت های اخیر و ایجاد تصاویری با قدرت تفکیک مکانی بالا، لزوم استفاده توام از اطلاعات طیفی و مکانی را در طبقه بندی تصاویر فراطیفی ایجاب می کند. در این تحقیق روشی جدید جهت طبقه بندی طیفیمکانی تصاویر فراطیفی به کمک الگوریتم جنگل پوشای مینیمم ( msf) مبتنی بر نشانه ها که یکی از دقیق ترین الگوریتم ها در این زمینه است و تکنیک کاهش ابعاد معرفی می شود. در روش پیشنهادی تاثیر کاهش ابعاد تصاویر فراطیفی به کمک الگوریتم ژنتیک در سه مرحله قبل و بعد از انتخاب نشانه ها و به صورت همزمان بررسی می گردد. در این مطالعه نشانه ها از روی نقشه طبقه بندی ماشین بردار پشتیبان ( svm) انتخاب شدند. روش پیشنهادی بر روی سه تصویر فراطیفی pavia، telops و indian pines پیاده سازی گردید، نتایج آزمایشات بدست آمده برتری به کارگیری الگوریتم ژنتیک را قبل از انتخاب نشانه ها در تصاویر pavia و telops نشان می دهد. در تصویر indian pines کاهش ابعاد در هر دو مرحله قبل و بعد از انتخاب نشانه ها و به صورت همزمان موجب افزایش دقت طبقه بندی می گردد.

Improved Spectral-Spatial Classification Minimum Spanning Forest by Reducing the Spatial Dimensions of Hyperspectral Images

Imaging spectroscopy, also known as hyperspectral imaging, is concerned with the measurement, analysis, and interpretation of spectra acquired from either a given scene or a specific object at a short, medium, or long distance by a satellite sensor over the visible to infrared and sometime thermal spectral regions. The recent developments in spatial, spectral and radiometric resolution of hyperspectral images have stimulated new methodologies for land cover and land use classification. There are two major approaches for classification of hyperspectral images: the spectral or pixelbased and the spectralspatial or objectbased approaches. While the pixelbased techniques use only the spectral information of the pixels, the spectralspatial frameworks employ both spectral characteristics and spatial context of the pixels. The pixelbased classification methods are often unable to accurately differentiate between some classes with high spectral similarity. This is mainly because they employ only the spectral information in order to identify different land covers. Consequently, methods that can exploit the spatial information are essential for more accurate classification results.Among the various methods for extracting spatial information, segmentation techniques are the powerful tools for defining the spatial dependences among the pixels and finding the homogeneous regions in the image. An alternative way to achieve the accurate segmentations of image is markercontrolled segmentation. The idea behind this approach is selecting of one or several pixels for every spatial object as the seed or a marker of the corresponding region. The markerbased segmentation significantly reduced the oversegmentation problem and led to better accuracy rate. Recently, an effective approach to spectralspatial classification of hyperspectral images has been proposed based on Minimum Spanning Forest (MSF) grown from automatically selected markers using Support Vector Machines (SVM) classification. In this framework, a connected components labelling is applied on the classification map. Then, if a region is large enough, its marker is determined as the P% of pixels within this region with the highest probability estimates. Otherwise, it should lead to a marker only if it is very reliable. A potential marker is formed by pixels with estimated probability higher than a defined threshold.This paper aims at improving this approach by reducing the spatial dimensions of hyperspectral images. The proposed approach are evaluated the dimension reduction of hyperspectral image before and after marker selection process in MSF using genetic algorithm. The genetic algorithm is a general adaptive optimization search method based on a direct analogy to Darwinian natural selection and genetics in biological systems. It starts from an initial population which is composed of a set of possible solutions called individuals (chromosomes), and then evaluates the quality of each individual based on a fitness function. We use the Kappa coefficient accuracy parameter of SVM classification obtained from the training samples subset as the fitness function. Three benchmark hyperspectral datasets are used for evaluation: the Pavia dataset, the Telops dataset and the Indian Pines dataset. Experimental results show the superiority of using genetic algorithm before selecting markers in Pavia and Telops datasets. In Indian Pines dataset, the classification accuracy was increased with reduced dimensions both before and after the marker selection and concurrently.