杨贵军, 万 鹏, 于海洋, 徐 波, 冯海宽. 无人机多光谱影像辐射一致性自动校正[J]. 农业工程学报, 2015, 31(9): 147-153. DOI: 10.11975/j.issn.1002-6819.2015.09.023
    引用本文: 杨贵军, 万 鹏, 于海洋, 徐 波, 冯海宽. 无人机多光谱影像辐射一致性自动校正[J]. 农业工程学报, 2015, 31(9): 147-153. DOI: 10.11975/j.issn.1002-6819.2015.09.023
    Yang Guijun, Wan Peng, Yu Haiyang, Xu Bo, Feng Haikuan. Automatic radiation uniformity correction of multispectral imagery acquired with unmanned aerial vehicle[J]. Transactions of the Chinese Society of Agricultural Engineering (Transactions of the CSAE), 2015, 31(9): 147-153. DOI: 10.11975/j.issn.1002-6819.2015.09.023
    Citation: Yang Guijun, Wan Peng, Yu Haiyang, Xu Bo, Feng Haikuan. Automatic radiation uniformity correction of multispectral imagery acquired with unmanned aerial vehicle[J]. Transactions of the Chinese Society of Agricultural Engineering (Transactions of the CSAE), 2015, 31(9): 147-153. DOI: 10.11975/j.issn.1002-6819.2015.09.023

    无人机多光谱影像辐射一致性自动校正

    Automatic radiation uniformity correction of multispectral imagery acquired with unmanned aerial vehicle

    • 摘要: 针对一个架次内无人机影像由于光照度变化、拍摄角度等原因引起的相同地物点在不同影像上的辐射信息不一致的问题,验证了利用SIFT(scale invariant feature transform)算法匹配同名点,然后利用同名点灰度值的相关关系建立校正模型,再用该校正模型校正整幅影像的辐射一致性校正方法。对比评价了基于直方图匹配的色彩一致性校正方法、原始色彩空间辐射一致性校正、针对三波段影像的HSV(hue,saturation,value)色彩空间亮度一致性校正以及双边滤波去噪的效果。试验结果表明:基于直方图匹配的色彩一致性校正能在视觉上达到很好的效果,但是会造成校正后影像的灰度级严重缺失;基于同名点灰度值相关关系的校正模型能够很好地恢复待校正影像与基准影像的辐射一致性;HSV色彩空间亮度一致性校正能够在色彩上和辐射信息上与基准影像均达到很好的一致性,但只适用于三波段影像;双边滤波在去除噪声的同时,能够保持甚至提高校正后影像与基准影像的辐射一致性。

       

      Abstract: Abstract: Unmanned aerial vehicles (UAVs) are an exciting new remote sensing tool capable of acquiring high resolution spatial data. In a data acquisition task, hundreds of images are acquired in a sortie due to the very small footprint of each image. The gray-scale value of homonymous points in adjacent-image pairs which is gathered by unmanned aerial vehicle in a sortie should be consistent on an -idealized condition. Actually, the gray-scale value of homonymous points always yields different results due to changes in illuminance, different shooting angle etc. In this study, we described a methodology for radiation uniformity correction among different images. The first step of the methodology was matching the images by scale invariant feature transform (SIFT) feature detector to extract homonymous points from which its gray-scale value in different images could be used to establish correlative function in the next step. The uncorrected image then was corrected by the correlative function. We also proposed a radiation uniformity correction workflow of adjacent-image pairs and image sequences. In the area of photogrammetry, the color consistency in visual form was more emphasized and many dodging method was proposed. But those methods can not be utilized in remote sensing application which emphasizes the radiation uniformity. In this paper, the color consistency adjusting based on histogram matching, the radiation uniformity correction in the original color space and the luminance consistency correction in the hue-saturation-value (HSV) color space in allusion to three-channel images was performed and the results was compared among those methods. The experimental results indicated that the color consistency correction based on histogram matching method can obtain a very good effect visually, but can also lead to severe grayscale gap. The radiation uniformity correction in the original color space was capable of achieving radiation consistency,but had little chromatic aberration in some case. The luminance consistency adjusting in the HSV color space was able to obtain a great result both visually and in radiation consistency, but the method was limited in utilization of three-channel images. The noise was enhanced after correction in some case. The bilateral filter was used to remove the noise, concurrently to retain radiation consistency between corrected image and reference image. The last part of this paper described the limitation of our method and indicated the needs for further studies. Also the processing chain of image sequences was proposed. Propagation of errors may cause more aberration at the image which far from reference image. So, the block adjustment may be considered into next step studies. In addition to this, SIFT algorithm was a time consuming method for this single target. So, we can integrate radiation uniformity correction into aero triangulation, both of which need feature extraction. Finally, the effect of sensor calibration on radiation uniformity correction should be studied in the future.

       

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