Journal of Geo-information Science >
Effects of Spatial Resolution and Texture Features on Multi-spectral Remote Sensing Classification
Received date: 2017-05-05
Request revised date: 2017-09-24
Online published: 2018-01-20
Supported by
National Natural Science Foundation of China, No.41771370;High-resolution Earth Observation System Project of China, No.30-Y20A29-9003-15/17, 03-Y20A04-9001-15/16, 03-Y20A04-9001-17/18;National Key R&D Program of China, No.2017YFD0600903.
Copyright
Multi-spectral remote sensing classification is strongly affected by spatial resolution while the classification accuracy is not necessarily improved by the increase of the spatial resolution. There exists an optimal resolution for each geographical entity, corresponding to its intrinsic spatial and spectral characteristics. Despite of many existing efforts, it is still far from clear how spatial resolutions affect classification accuracy. In recent studies, texture feature has been widely used as an effective factor to increase the classification accuracy of multi-spectral remote sensing. As an important characteristic of spatial information, texture feature is closely linked with morphology and distribution of objects. It may greatly increase classification accuracy in some cases that the same object has different spectra or different objects have the same spectrum. However, large uncertainties still exist in the effects of texture feature on classification for various objects at different spatial scales. This paper presents a case study implemented in Jining, Shandong Province to examine the impacts of spatial resolution and texture features on Multi-spectral Remote Sensing Images Classification using the Chinese Gaofen-1 (GF-1) satellite data. The GF-1 satellite was successfully launched on April 26, 2013, which was equipped with two types of sensors. One is the wide field view sensor (WFV sensor); the other is the panchromatic and multispectral sensor (PMS sensor) which can acquire panchromatic images at 2 m spatial resolution and multispectral images at 8 m spatial resolution. First, we carried out radiometric calibration, atmospheric correction and precise geometric rectification for original images. Then, we conducted data fusion based on Gram-Schmidt transformation and performed the expansion of spatial scales for the establishment of the spatial series of the reflectance (2~10 m at an interval of 1 m, 10~90 m at an interval of 10 m). Second, we generated the classification results using three popular approaches, i.e., the Maximum Likelihood Classification (MLC), the Support Vector Machine (SVM) and the Artificial Neural Network (ANN). Third, after the calculation of texture features of 2 m and 8 m for reflectance images, separately, the Principal Components Analysis (PCA) method was used for texture features selection. The data combining key features with corresponding multi-spectral bands were classified based on the ANN approach. Finally, we evaluated the classification accuracies using the confusion matrix. Our final regression analysis suggested an optimal spatial resolution of 5 m for the multi-spectral classification, implying that the optimal selection of the spatial resolution is not affected by the spectral information of multi-spectral remote sensing images. Further analysis of changing trend of accuracies along with spatial resolution showed a sharp decrease when the spatial resolution is coarser than 20-30 m. The results of the impacts of texture feature suggested that, compared with the classification by spectral information, the accuracies of winter wheat, architecture, forest and water were increased by 1.49%, 1.51%, 4.94% and 1.54% at 2 m resolution, and 2.95%, 10.95%, 5.91% and 5.14% at 8 m resolution, respectively, when the texture features were introduced. We concluded that, compared with the classification accuracy of the spectral information, considering texture feature effects may improve the classification accuracies, to varying degrees, at different spatial resolutions, especially when an appropriate resolution was chosen. Our findings are practically helpful for the optimal selection of spatial resolution for multi-spectral remote sensing classification. In the next step, we will further examine the impacts of spatial resolution and texture features at larger scales. In addition, the impacts of texture features at different phenological stages will also be investigated.
YANG Yanjun , TIAN Qingjiu , ZHAN Yulin , TAO Bo , XU Kaijian . Effects of Spatial Resolution and Texture Features on Multi-spectral Remote Sensing Classification[J]. Journal of Geo-information Science, 2018 , 20(1) : 99 -107 . DOI: 10.12082/dqxxkx.2018.170177
Fig. 1 The map of the study area图1 研究区概况 |
Tab. 1 Sample numbers表1 样本数量 |
类别 | 样本 | |
---|---|---|
训练样本 | 验证样本 | |
冬小麦 | 120 | 804 |
有林地 | 90 | 413 |
水体 | 98 | 130 |
人工建筑 | 80 | 330 |
总计 | 388 | 1677 |
Fig. 2 Jeffreys-Matusita distance of four typial classes at different spatial resolutions图2 不同空间分辨率下4种地物之间的JM值 |
Fig. 3 Jeffreys-Matusita distance of four typial classes at 2 m and 8 m spatial resolutions图3 2 m和8 m分辨率下4种地类之间的JM值 |
Fig.4 Overall accuracy of the classification for three methods at different spatial resolutions图4 3种分类方法的总体精度曲线及相应趋势线 |
Fig.5 Classification results before and after introducing texture features at 2 m and 8 m spatial resolution图5 2 m和8 m分辨率下纹理特征加入前后的分类结果图 |
Tab. 2 Classification accuracy of four classes表2 4种典型地类的分类精度 |
数据类别 | OA/% | Kappa系数 | 冬小麦/% | 有林地/% | 水体/% | 人工建筑/% | |||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|
PA | UA | PA | UA | PA | UA | PA | UA | ||||||
2 m反射率 | 91.95 | 0.8789 | 93.91 | 94.49 | 89.10 | 82.33 | 96.92 | 94.03 | 88.79 | 98.65 | |||
2 m反射率_纹理 | 93.62 | 0.9000 | 95.40 | 95.76 | 91.28 | 87.27 | 98.46 | 89.51 | 90.30 | 99.00 | |||
8 m反射率 | 90.59 | 0.8585 | 93.03 | 94.44 | 88.94 | 78.19 | 96.92 | 94.03 | 84.19 | 98.58 | |||
8 m反射率_纹理 | 93.64 | 0.9100 | 92.78 | 97.39 | 94.84 | 84.10 | 91.54 | 99.17 | 95.14 | 96.31 |
Fig. 6 Accuracy changes of four classes before and after adding texture features图6 添加纹理特征前后各地物的精度变化 |
The authors have declared that no competing interests exist.
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