基于多時相點云的貼金石質文物病害檢測
本文選題:多時相點云 + 金箔病害; 參考:《北京建筑大學》2013年碩士論文
【摘要】:對于貼金石質文物的修復工作,最為重要的是對金箔的修復,這種工作難度大,工序復雜,費時較長,且耗資巨大。例如重慶大足寶頂山貼金千手觀音造像的修復,單單金箔修復的工序就有二十幾道,歷時六年,耗資千萬。因此對于貼金石質文物的保護,一個非常重要的方面就是對金箔的有效保護,而其前提是對金箔病害進行有效的病害檢測。本文正是以此為切入點,利用三維激光掃描技術,通過采集多時相的點云數(shù)據(jù),進行多時相點云的對比檢測,從而發(fā)現(xiàn)金箔的病害并量算病害面積,,為后續(xù)文物修復與保護工作提供數(shù)據(jù)支撐。 貼金石質文物病害提取的一個關鍵就是確定病害的發(fā)生閾值。本文在分析病害閾值組成的基礎上,導出了病害閾值的公式,并從儀器誤差、數(shù)據(jù)采集誤差與數(shù)據(jù)處理誤差三個方面進行了系統(tǒng)的分析,從而指出了提高點云精度應采取的具體措施。 貼金石質文物病害檢測采用部分Hausdorff距離做為核心算法,基于病害發(fā)生閾值,對病害區(qū)域進行提取與標示。由于部分Hausdorff距離需要對整個點集進行運算,比較耗時。而線性八叉樹是點云數(shù)據(jù)處理中一種較為常用的數(shù)據(jù)組織方式,該方式層次清楚,編碼簡單,占用內存小,若利用線性八叉樹對點云數(shù)據(jù)進行組織,則對其鄰域點云進行檢索、運算即可。因此,本文提出了利用線性八叉樹對點云進行組織的方法。在線性八叉樹的基礎上對編碼方式進行了改進,將八進制的編碼方式轉換為自然數(shù)進行索引,提高了檢索的效率。針對剖分層次的限制,提出了改進的剖分方式,提高了內存的利用率。 在文物實際保護工作中,只給出病害的區(qū)域還不夠。因此,本文提出了利用病害面積對病害區(qū)域進行量算的方法。利用三角格網(wǎng)模型面積對實物表面進行逼近,提出基于病害區(qū)域三角格網(wǎng)的搜索算法,利用海倫公式計算病害區(qū)域的面積。本文利用開發(fā)的貼金石質文物病害檢測試驗原型系統(tǒng),以重慶大足寶頂山千手觀音造像為試驗對象,對提出的算法流程進行了驗證,證明了本算法流程在貼金石質文物病害檢測領域的可行性。
[Abstract]:The restoration of gold foil is the most important work for the restoration of gold stony relics. This kind of work is difficult, complex, time-consuming and costly. For example, there are more than 20 gold foil restoration procedures for the restoration of the gold thousand hands Guanyin statue on the Dazu Baoding Mountain in Chongqing, which lasted for six years and cost tens of millions of dollars. Therefore, an important aspect of the protection of gold foil is the effective protection of gold foil, which is based on the effective disease detection of gold foil. In this paper, by using 3D laser scanning technology and collecting multi-temporal point cloud data, we can find out the damage of gold foil and calculate the area of the disease. To provide data support for the subsequent restoration and protection of cultural relics. A key to the extraction of the disease is to determine the threshold of the disease. On the basis of analyzing the composition of disease threshold, the formula of disease threshold is derived, and the error of instrument, data acquisition and data processing are analyzed systematically. The concrete measures to improve the accuracy of point cloud are pointed out. Partial Hausdorff distance is used as the core algorithm to detect the disease of gold paste stone relics. Based on the threshold of disease occurrence, the disease area is extracted and marked. Because part of the Hausdorff distance needs to operate on the whole set of points, it is time consuming. The linear octree is a common data organization method in point cloud data processing. This method has the advantages of clear level, simple coding and small memory. If the linear octree is used to organize the point cloud data, the neighborhood point cloud can be retrieved. Operation is sufficient. Therefore, a method of organizing point clouds using linear octree is proposed. On the basis of linear octree, the coding method is improved, the octal coding method is converted to natural number for index, and the efficiency of retrieval is improved. Aiming at the limitation of partition level, an improved partition method is proposed to improve the utilization of memory. In the actual protection of cultural relics, it is not enough to give only the area of disease. Therefore, this paper puts forward a method to calculate the disease area by using disease area. The triangular grid model area is used to approximate the real surface, and a search algorithm based on the triangular grid of the disease region is proposed. The area of the disease area is calculated by using Helen's formula. In this paper, a prototype system for disease detection of gold-coated stone relics is developed, and the proposed algorithm flow is verified by taking the Qianhand Guanyin image of Dazu Baoding Mountain in Chongqing as the experimental object. It is proved that this algorithm is feasible in the field of disease detection of gold-coated stone relics.
【學位授予單位】:北京建筑大學
【學位級別】:碩士
【學位授予年份】:2013
【分類號】:G264.3;P225.2
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