【摘要】：近年來,無人機低空航測正逐步成為與衛(wèi)星遙感、常規(guī)航空攝影測量相并列的航空遙感技術(shù),其主要目標是為了滿足現(xiàn)代社會對于及時測繪和精細測繪的應用需求。盡管具有及時性、精確性的優(yōu)點,但通常需等待無人機降落之后才能獲取傳感器系統(tǒng)所拍攝的影像數(shù)據(jù),無法滿足對及時性要求極高的應急測繪需求。針對這一問題,將數(shù)碼攝像機集成于傳感器系統(tǒng)中,并利用無線傳輸技術(shù)將拍攝的視頻進行實時下傳。然而,受制于視頻圖像的小像幅,小視場、低分辨率、無法直觀反映測區(qū)整體概況等缺陷,限制了其潛在的應用價值。因此,研究利用航空視頻進行正射影像制作這一新興領(lǐng)域,具有迫切的應用需求及研究價值。 將航空視頻拼接為正射影像主要涉及兩方面內(nèi)容：第一,如何將動態(tài)的視頻數(shù)據(jù)轉(zhuǎn)換為靜態(tài)的幀圖像數(shù)據(jù)；第二,如何利用無初始位置信息的幀圖像數(shù)據(jù)進行正射影像制作。針對第一個問題,需研究視頻圖像的提取技術(shù),同時提取的幀圖像之間,其重疊度需滿足影像拼接要求。第二個問題則可分為兩個子問題加以解決。首先恢復幀圖像的空間結(jié)構(gòu),即影像在拍攝時空中的位置和姿態(tài)信息。其次,對恢復姿態(tài)后的影像進行正射糾正、拼接生成幾何位置一致、顏色變化平滑的正射影像。因此,本文的研究工作及創(chuàng)新之處主要體現(xiàn)在： (1)首先,系統(tǒng)的總結(jié)了2D和3D至2D的影像幾何變換模型,并分析了兩種模型的幾何精度差異。其次,在給出兩種模型參數(shù)估計方法的基礎(chǔ)上,結(jié)合兩種模型的技術(shù)特點、幾何精度及應用需求,設(shè)計了基于像方和基于物方的兩種正射影像拼接流程。 (2)研究了攝像機的靜態(tài)幾何檢校方法及流程。首先,在分析數(shù)碼攝像機畸變規(guī)律基礎(chǔ)上,通過對比經(jīng)典的畸變模型與Brown模型的關(guān)系,提出了一種顧及高階項和交叉項的畸變模型,使攝像機的靜態(tài)總體檢校精度小于0.5個像元。其次,詳細推導了數(shù)碼攝像機的檢校流程,并對提出的畸變模型檢校結(jié)果進行分析,指出本文所提畸變模型的有效性。 (3)基于曲線擬合原理,提出一種自適應的關(guān)鍵幀提取方法。在分析UAV載航空視頻重疊度變化規(guī)律的基礎(chǔ)上,提出一種兩步法關(guān)鍵幀提取算法：即學習階段和提取階段。學習階段主要計算當前地形及飛行條件下,視頻重疊度的變化規(guī)律。提取階段主要依據(jù)學習階段提供的初始值,在特定區(qū)間內(nèi)進行重疊度抽樣,并根據(jù)抽樣結(jié)果對該范圍內(nèi)的重疊度變化規(guī)律進行曲線擬合,進而按照擬合結(jié)果計算滿足重疊度需求的幀索引位置。 (4)針對運動像移所造成的影像模糊,研究利用圖像處理的方法對其進行恢復,獲取清晰影像。首先,詳細總結(jié)了目前國內(nèi)外關(guān)于核函數(shù)估計及影像去模糊處理的研究進展。其次,基于信息熵、信噪比、信息量等信息論測度,建立影像的有參和無參評價指標體系。最后以地面試驗及空中試驗結(jié)果為指導,提出適合視頻幀圖像的運動像移恢復策略。 (5)提出一種基于像方的影像空間結(jié)構(gòu)恢復及優(yōu)化方法。通過分析基于像方的影像轉(zhuǎn)換模型及其誤差傳播規(guī)律,針對幀圖像無POS信息的特點,提出一種利用連接點屬性將新加入影像逐漸納入到已經(jīng)優(yōu)化后影像序列中的結(jié)構(gòu)恢復方法,并通過最小二乘原理將累計的誤差合理配置于所有參與平差的影像中,使所有像點的總體投影誤差最小。最后,通過試驗結(jié)果驗證了本文方法的有效性。 (6)提出一種CPU與GPU協(xié)同處理的航空視頻拼接流程。針對航空視頻拼接的及時性需求,總結(jié)國內(nèi)外關(guān)于遙感數(shù)據(jù)的并行處理研究進展,提出利用GPU技術(shù)對視頻拼接的關(guān)鍵步驟進行并行加速,并根據(jù)CPU模式與GPU模式的特點,設(shè)計了利用兩種處理器進行協(xié)同操作的拼接流程。 (7)通過具體的工程實例,闡述了航空視頻拼接的作業(yè)流程,展示了相關(guān)的處理成果,并分析對比了像方和物方的拼接影像,指出兩種方法的優(yōu)缺點,驗證了本文以航空視頻進行正射影像制作的可行性。 本文以研究解決利用航空視頻進行正射影像制作過程中的關(guān)鍵技術(shù)為研究目的,結(jié)合攝像機檢校、關(guān)鍵幀提取、運動像移恢復、影像空間結(jié)構(gòu)重建、GPU并行運算等關(guān)鍵技術(shù),利用關(guān)鍵幀圖像完成了基于像方和基于物方的正射影像制作,拓展了航空視頻的應用范圍。
[Abstract]:In recent years, the low-altitude aerial survey of the unmanned aerial vehicle is becoming an aerial remote sensing technology which is parallel to the satellite remote sensing and the conventional aerial photogrammetry, and the main aim is to meet the application demand of the modern society for timely mapping and fine mapping. Although it has the advantages of timeliness and accuracy, it is generally necessary to wait for the unmanned aerial vehicle to land, acquire the image data taken by the sensor system, and can not meet the emergency mapping requirement with high requirements for timeliness. Aiming at the problem, the digital video camera is integrated in the sensor system, and the captured video is transmitted in real time by the wireless transmission technology. However, the small image, small field of view and low resolution, which are subject to the video image, can not directly reflect the overall situation of the survey area and other defects, and limit its potential application value. Therefore, the research of using aerial video to make the orthophoto image to make this new field, has the urgent application requirement and the research value. The method comprises the following steps of: firstly, converting the dynamic video data into static frame image data; secondly, using the frame image data without the initial position information to perform the orthophoto-image system; For the first problem, the extraction technology of the video image needs to be studied, and the overlapping degree of the extracted frame images is to meet the image splicing requirements. The second question can be divided into two sub-problems. The first step is to restore the spatial structure of the frame image, that is, the position and attitude of the image in the air at the time of the shooting. and then, the image after the restoration attitude is corrected, the geometric position of the splicing generation is consistent, and the color change is smooth and the positive projection As a result, the research work and innovation of this paper are mainly embodied in this paper. (1) Firstly, the geometric transformation model of 2D and 3D-2D is summarized, and the geometry of the two models is analyzed. Secondly, on the basis of the two model parameter estimation methods, the two kinds of positive projective images based on the image side and the object side are designed in combination with the technical characteristics, the geometric precision and the application requirement of the two models. Connected to the process. (2) The static geometric calibration of the camera is studied. In this paper, based on the analysis of the distortion law of digital camera, a kind of distortion model, which takes into account the high-order terms and cross terms, is put forward based on the analysis of the distortion law of the digital camera, so that the accuracy of the static total physical examination of the camera is less than 0. . Secondly, the calibration process of the digital camera is derived in detail, and the result of the proposed distortion model is analyzed, and the distortion model proposed in this paper is pointed out. The validity of the model is based on the principle of curve fitting. In this paper, a two-step method of key-frame extraction is proposed based on the analysis of the variation law of the degree of overlap of UAV-loaded aerial video. Stage and extraction phase. The learning phase mainly calculates the current terrain and flight conditions, and the video is heavy The extraction stage is mainly based on the initial value provided in the learning phase, the overlap degree sampling is carried out in a specific interval, and the variation law of the overlap degree in the range is curve-fitted according to the sampling result, and the overlapping degree needs to be met according to the fitting result. (4) image blurring caused by moving image, and the method of image processing is used to study it. Restore and get a clear image. First of all, a detailed summary of the current home and abroad about kernel function estimation and image The research progress of fuzzy processing is based on information theory measure of information entropy, signal-to-noise ratio, information quantity and so on. and finally, based on the ground test and the air test result, a suitable video frame image is proposed, And (5) a video-based image is proposed. The spatial structure recovery and optimization method is presented. By analyzing the image-based image transformation model and its error propagation law, a new image is gradually incorporated into the optimized image by using the attribute of the connection point, aiming at the characteristics of the image-free information of the frame image. The structure recovery method in the image sequence is adopted, and the accumulated error is reasonably arranged in the image of all the participating adjustment by the least square principle, so that all the images The overall projection error of the image point is minimal. Finally, by the test results The effectiveness of this method is verified. (6) A kind of CPU and GPU are put forward. In this paper, the research progress of parallel processing of remote sensing data at home and abroad is summarized, and the key steps of video splicing are accelerated in parallel by using GPU technology. The characteristics of the PU mode and the GPU mode are designed. (7) The operation flow of the aviation video splicing is described through the specific project examples, and the relevant processing results are shown, and the comparison of the image and the object side is also analyzed. The image is spliced and the advantages and disadvantages of the two methods are pointed out. The feasibility of making a positive projection image of an empty video is presented in this paper. The key technologies in the process of using aerial video to make the orthophoto image are studied, and the camera calibration, the key frame extraction, the motion image removal and the image space are combined. The key technologies such as structure reconstruction, GPU parallel operation and other key technologies are used to complete the image-based and object-based direct injection by using the key frame images.
【學位授予單位】：武漢大學
【學位級別】：博士
【學位授予年份】：2014
【分類號】：P231

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本文編號：2509599