A COMPARISON OF THE PERFORMANCE OF PIXEL-BASED AND OBJECT-BASED CLASSIFICATIONS OVER IMAGES WITH VARIOUS SPATIAL RESOLUTIONS
A COMPARISON OF THE PERFORMANCE OF PIXEL-BASED AND OBJECT-BASED CLASSIFICATIONS OVER IMAGES WITH VARIOUS SPATIAL RESOLUTIONS
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发表时间：
2008
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通讯作者：
Y. Gao;J. Mas
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作者：
Y. Gao;J. Mas
在过去的二十年里，计算机技术，地球观测传感器和GIS科学的进步，导致了“基于对象的图像分析（OBIA）”作为传统的基于像素的图像分析方法的替代品的发展。传统的基于像元的图像分析方法存在局限性，主要原因是：图像像元不是真正的地理对象，像元拓扑结构有限，基于像元的图像分析在很大程度上忽略了空间的图像解释元素，如纹理、背景和形状;高空间分辨率图像中隐含的增加的可变性使传统的基于像素的分类器混淆，导致分类精度降低（Hay and Castilla 2006）。与基于像素的分类方法不同，OBIA方法是针对图像分割产生的（同质）对象，可以使用更多的元素进行分类。由于目标是一组像素，因此可以计算目标特征，如平均值、标准差、比率等;此外，还有目标的形状和纹理特征，可用于区分具有相似光谱信息的土地覆盖类别。这些额外类型的信息使OBIA有可能制作比传统的基于像素的方法制作的精度更高的土地覆盖专题图。在本文中，我们期待在不同的空间分辨率的卫星图像的OBIA的性能，比较的分类结果与那些产生的基于像素的方法，我们打算找出如何空间分辨率的卫星图像的影响OBIA的性能。实验结果表明，在4种不同空间分辨率的两组图像上，基于目标的图像分析比基于像素的图像分析获得了更高的精度;随着空间分辨率的增加，基于目标的图像分析与基于像素的图像分析的精度差异逐渐减小。结果表明，基于地物的遥感影像分析比基于像元的遥感影像分析具有优势，在精度等级上，这种优势在高空间分辨率的卫星影像上表现得更好。* 通讯作者。
In the last two decades, advances in computer technology, earth observation sensors and GIS science, led to the development of “Object-based Image Analysis (OBIA)” as an alternative to the traditional pixel-based image analysis method. It was recognized that traditional pixel-based image analysis is limited because of the following reasons: image pixels are not true geographical objects and the pixel topology is limited; pixel based image analysis largely neglects the spatial photo-interpretive elements such as texture, context, and shape; the increased variability implicit within high spatial resolution imagery confuses traditional pixel-based classifiers resulting in lower classification accuracies (Hay and Castilla 2006). Different from pixel-based method, OBIA works on (homogeneous) objects produced by image segmentation and more elements can be used in the classification. As an object is a group of pixels, object characteristics such as mean value, standard deviation, ratio, etc can be calculated; besides there are shape and texture features of the objects available which can be used to differentiate land cover classes with similar spectral information. These extra types of information give OBIA the potential to produce land cover thematic maps with higher accuracies than those produced by traditional pixel-based method. In this paper, we look at the performance of OBIA with different spatial resolution satellite images; comparing the classification results with those produced by the pixel-based method, we intend to find out how spatial resolution of satellite images influences the performance of OBIA. Experiment results showed that with the two sets of images of four different spatial resolutions, object based image analysis obtained higher accuracies than those of the pixel based one; with the increasing of the spatial resolution, the difference in accuracy values between object based and pixel based is decreasing. This paper showed that the object-based image analysis has advantage over the pixel-based one, and in accuracy rating, the advantage was better represented by higher spatial resolution satellite images. * Corresponding author.