攝影測量外文文獻(xiàn)及譯文

1、蘇州科技學(xué)院本科生畢業(yè)設(shè)計(jì)（論文）數(shù)字?jǐn)z影測量和激光掃描文化遺產(chǎn)文檔的一體化 奧爾莎娃卜克赫*葉海亞 哈拉諾伯特德國斯圖加特大學(xué)攝影測量學(xué)院 斯圖加特兄妹大街24D,D-70174 yahyashawifp.uni-stuttgart.de委員會(huì)V4工作組關(guān)鍵詞：文化遺產(chǎn)，攝影測量，激光掃描，融合，線性表面特征，半自動(dòng)化摘要： 本文在結(jié)合地面激光掃描和近景攝影測量文物古跡文件的潛力進(jìn)行了討論。除了改進(jìn)了的幾何模型，一體化的目的是支持在歷史場景中如邊緣和縫隙的線性特性的視覺質(zhì)量。雖然激光掃描儀提供了非常豐富的表面細(xì)節(jié)，但是它并沒有提供足夠的數(shù)據(jù)來構(gòu)造被掃描物體的所有表面特征的輪廓，即使他們在現(xiàn)實(shí)

2、中都有清晰的輪廓。在地物邊緣和線性上的信息是基于圖像的分析。為此目的一個(gè)基于圖像數(shù)據(jù)的集成分割過程將支持對(duì)象的幾何信息從激光數(shù)據(jù)的提取。該方法適用于基于圖像的半自動(dòng)化技術(shù)以填補(bǔ)激光掃描數(shù)據(jù)的空白，并添加新的細(xì)節(jié)，這就要求建立現(xiàn)場體積更現(xiàn)實(shí)的感知。實(shí)驗(yàn)的調(diào)查與實(shí)施是基于從艾爾卡茲尼寶庫獲得的數(shù)據(jù)，一個(gè)在約旦佩特拉著名的紀(jì)念碑。1、 緒論 在文物古跡的文檔中經(jīng)常需要生成歷史建筑物的三維模型。即旅游的目的是為學(xué)生和研究人員提供教育資源。在這些模型生成過程中，要求高幾何精度，所有信息的可用性，模型中的尺寸大小和影像寫實(shí)效率必須通過不用的數(shù)據(jù)收集方法來滿足埃爾-哈基姆等人，2002。近景攝影測量是一個(gè)在

3、遺產(chǎn)文檔的背景下經(jīng)常采用且廣為接受的技術(shù)格魯恩等人，2002和德貝韋茨，1996。在過去的十年中，這些傳統(tǒng)的陸地方法也受益于這樣一個(gè)事實(shí):用單架相機(jī)進(jìn)行數(shù)字圖像采集現(xiàn)在是可行的。因此，攝影測量數(shù)據(jù)采集的效率可以通過基于數(shù)字圖像處理的自動(dòng)工具的集成大大改善。此外，激光掃描已成為高質(zhì)量的3D模型的文化遺產(chǎn)和歷史建筑生成三維數(shù)據(jù)采集的標(biāo)準(zhǔn)工具伯勒爾和馬布斯，2002。這些系統(tǒng)允許快速和可靠的生成根據(jù)反射的光脈沖的運(yùn)行時(shí)數(shù)以百萬計(jì)的三維點(diǎn)。這將使得可以在一個(gè)非常有效和密集的幾何形狀表面進(jìn)行測量。關(guān)于測量速率目前的局限性，準(zhǔn)確性，或空間點(diǎn)的密度在不久的將來進(jìn)一步的消失，因此，激光掃描似乎成為三維文件及遺

4、產(chǎn)的生成演示占主導(dǎo)地位的方法。盡管這些方法有重大的進(jìn)展，但是還存在一定的局限性，這對(duì)最終的三維模型的質(zhì)量會(huì)產(chǎn)生影響。盡管目前的激光掃描儀可以快速，可靠地產(chǎn)生大量的點(diǎn)云，但這個(gè)數(shù)據(jù)的分辨率仍然是不充分，特別是邊緣和線性地物是否被收集。相反，數(shù)字?jǐn)z影測量是在輪廓再現(xiàn)更準(zhǔn)確的，特別是如果他們在現(xiàn)實(shí)中輪廓分明的情況下。另一方面，對(duì)于表面含有不規(guī)則的和無標(biāo)記的幾何細(xì)節(jié)的部分圖像單獨(dú)建模困難的，甚至不切實(shí)際。另外，可以手動(dòng)或半自動(dòng)識(shí)別被測點(diǎn)，但這是一個(gè)漫長而繁瑣的工作，特別是如果有相當(dāng)數(shù)量的點(diǎn)被捕獲。如果數(shù)據(jù)收集是從不同的角度實(shí)現(xiàn)的，才能保證像文物古跡空間復(fù)雜對(duì)象的完全覆蓋。盡管這在大多數(shù)情況下是可能的，

5、但問題可能會(huì)導(dǎo)致一個(gè)事實(shí)，即建立和拆卸完成激光系統(tǒng)是相對(duì)耗時(shí)的。與之相反，這種嘗試用一個(gè)標(biāo)準(zhǔn)的數(shù)碼相機(jī)收集附加圖像幾乎可以忽略。此外,相對(duì)于激光掃描測量范圍在圖像集合的限制越來越少，為覆蓋該對(duì)象的完整結(jié)構(gòu)簡化了不同視點(diǎn)的選擇。出于這個(gè)原因，有利于完成一個(gè)已經(jīng)從激光測量的基礎(chǔ)上產(chǎn)生，從該范圍內(nèi)的數(shù)據(jù)獨(dú)立地捕捉強(qiáng)度圖像的幾何模型。通過這些方法幾何對(duì)象，基于攝影測量提供的范圍內(nèi)的數(shù)據(jù)由于閉塞是不可使用的。因此，如果這兩種技術(shù)在數(shù)據(jù)處理過程中被組合，那么數(shù)據(jù)采集的效率和靈活性達(dá)到最高程度將是可能的。在我們的方法這種融合有助于提高收集三維模型的幾何形狀和視覺質(zhì)量。在數(shù)據(jù)收集邊緣和類似裂紋線性地物信息是基

6、于從激光數(shù)據(jù)提供的對(duì)象的幾何信息圖像的分析。此外，不可訪問的激光數(shù)據(jù)掃描區(qū)域原因是由于被遮蓋，這就需要增加圖像的半自動(dòng)化評(píng)價(jià)。通過這些方法，現(xiàn)場一個(gè)完整的三維特征可以生成足夠清晰的細(xì)節(jié)。在本文所提出的方法是在一個(gè)項(xiàng)目針對(duì)三維虛擬模型的艾爾卡茲尼寶庫生成證明框架，就是在約旦佩特拉一座著名的紀(jì)念碑。第二節(jié)對(duì)采集和相關(guān)圖像預(yù)處理和激光雷達(dá)數(shù)據(jù)進(jìn)行了討論。這個(gè)預(yù)處理的要求主要是為了配準(zhǔn)激光和圖像數(shù)據(jù)以供進(jìn)一步處理。第三部分提出了我國模范特征提取方法用于艾爾卡茲尼寶庫左門的混合動(dòng)力系統(tǒng)。2、 數(shù)據(jù)采集和預(yù)處理在與約旦哈希姆大學(xué)合作進(jìn)行的數(shù)據(jù)的收集，它已經(jīng)用于我們的學(xué)術(shù)研究。其中一個(gè)項(xiàng)目的目標(biāo)是在約旦佩特

7、拉城艾爾卡茲尼寶庫紀(jì)念碑生成的三維文件，這是在如圖1所示。 圖1. 佩特尼艾爾卡茲尼寶庫正面2.1、艾爾卡茲尼紀(jì)念碑 古代納巴泰佩特拉城經(jīng)常被稱為古代的第八大奇跡。從公元前400年到公元106佩特拉城是約旦西南部繁榮的納巴泰帝國首都。佩特拉的廟宇，陵墓，劇院等建筑分布在400平方英里，這些建筑被雕刻成玫瑰色的砂巖峭壁。之后一個(gè)旅客進(jìn)入佩特拉，從山上一兩公里令人印象深刻的裂縫進(jìn)入佩特拉，第一門面被看作是艾爾卡茲尼寶庫，這被認(rèn)為是在佩特拉城最有名的古跡。艾爾卡茲尼寶庫正面是高40米,保存相當(dāng)完好,可能是因?yàn)樗拿荛]空間保護(hù)它免受侵蝕的影響。當(dāng)阿拉伯人叫它艾爾卡茲尼寶庫的時(shí)候，意味著路是過的駱駝商隊(duì)

8、的金庫或稅務(wù)局，而另一些人則認(rèn)為，艾爾卡茲尼寶庫紀(jì)念碑是一座墳?zāi)?。艾爾卡茲尼寶庫令人印象深刻的外觀背后，寬大的方形房間是用巖石雕刻出來的賽德采克，2000。2.2、傳感器應(yīng)用 對(duì)于點(diǎn)的采集，MENSI公司公司制造的三維激光掃描系統(tǒng)的gs100，法國已經(jīng)在應(yīng)用。掃描儀的特點(diǎn)是在水平方向360度視角，在垂直方向60度視角，使能夠?qū)崿F(xiàn)全景采集。測距是原理是由飛行測量基于綠色激光器532 nm處的時(shí)間來實(shí)現(xiàn)。該系統(tǒng)的掃描范圍允許測量距離是2至100米。掃描儀50米的距離的光斑大小為3毫米;距離單次測量的標(biāo)準(zhǔn)偏差為6毫米，該系統(tǒng)每秒能夠測量5000個(gè)點(diǎn)。在數(shù)據(jù)采集768X576像素分辨率的校準(zhǔn)視頻快照是

9、另外拍攝的，它會(huì)自動(dòng)映射到相應(yīng)的測量點(diǎn)。除了激光數(shù)據(jù)，數(shù)字圖像捕獲也使用富士S1相機(jī)的攝影測量處理，由于它提供了一個(gè)1536x2034像素分辨率和20毫米焦距。2.3、測量配置因?yàn)樵诎瑺柨ㄆ澞嵴婊趶膯蝹€(gè)站收集的數(shù)據(jù)不可能有一個(gè)完整的三維覆蓋率為，所以采用三個(gè)不同的視點(diǎn)與5次掃描來解決單站的遮擋。選擇的觀測點(diǎn)位置的問題作為調(diào)查這樣一個(gè)紀(jì)念碑的一個(gè)重要階段，因?yàn)闈撛诘膫鞲衅髡臼潜话瑺柨ㄆ澞嶂車嗌降沫h(huán)境限制。三個(gè)被選中的觀測點(diǎn)，一個(gè)在紀(jì)念碑的入口區(qū)，一個(gè)在紀(jì)念碑的左邊，最后一個(gè)掃描是從高出的觀測點(diǎn)收集。由于認(rèn)為從這些位置的激光掃描儀從一個(gè)掃描點(diǎn)的垂直領(lǐng)域不可能涵蓋所有的門面，左側(cè)和頂部掃描使用

10、來自同一個(gè)位置2個(gè)掃描點(diǎn)，考慮到擁有足夠的重疊區(qū)域，以便后續(xù)做整合?？偠灾?，五次掃描收集近500萬個(gè)點(diǎn)。所有獲得的三維模型都使用Innovmetric公司的PolyWorks軟件來處理。在一個(gè)獨(dú)立的坐標(biāo)系統(tǒng)合并五掃描到絕對(duì)坐標(biāo)系統(tǒng)得出艾爾卡茲尼外觀模型。使用點(diǎn)對(duì)應(yīng)的掃描登記后，軟件構(gòu)建了一個(gè)非冗余的表面表示，在被測物體的每一部分只是描述了一次。五個(gè)激光掃描的組合的結(jié)果如圖2，所生成的模型在平均每2厘米分辨率有超過1000萬個(gè)三角形。 圖2. 5個(gè)掃描所創(chuàng)建的艾爾卡茲尼的三維模型在額外的外部調(diào)查，一個(gè)360度的掃描儀在艾爾卡茲尼寶庫內(nèi)一個(gè)站點(diǎn)掃描了1900萬個(gè)點(diǎn)。圖3顯示了此次掃描的點(diǎn)云與覆蓋

11、顏色信息。圖3. 360度掃描的艾爾卡茲尼的內(nèi)部3、綜合數(shù)據(jù)處理盡管由激光掃描器產(chǎn)生的三維模型包含了大量描述表面的三角形，但仍然難以識(shí)別和定位的表面特征的輪廓。這種類型特征的一個(gè)圖像清晰可見的例子，如圖4所示。這個(gè)數(shù)據(jù)是從艾爾卡茲尼寶庫左側(cè)門收集的。它可以從相應(yīng)的三維視網(wǎng)狀模型如圖5所示看出，這些裂縫和邊緣輪廓是失去了在現(xiàn)有的激光數(shù)據(jù)的分辨率。 圖4.艾爾卡茲門左側(cè)為了支持這樣的細(xì)節(jié)的視覺質(zhì)量，一種從激光掃描儀和數(shù)字圖像數(shù)據(jù)組合的混合方法被開發(fā)。整合所有的數(shù)據(jù)集都是配準(zhǔn)在第一處理步驟。這是一種提取邊緣數(shù)據(jù)源對(duì)準(zhǔn)來實(shí)現(xiàn)的一種算法，這種算法是由科林乃克和弗里奇，2003提出來的。傳感器計(jì)算出后視定

12、向的參數(shù)后，從點(diǎn)云提供在現(xiàn)有的圖像缺失的第三維來生成距離圖像。最后，基于圖像數(shù)據(jù)的集成的分割過程被用于支持提取的細(xì)節(jié)和表面特征輪廓的距離圖像，加上，該方法適用于半自動(dòng)特征提取的圖像來縮小與激光掃描數(shù)據(jù)的差距。通過這些方式可以添加必要的細(xì)節(jié)產(chǎn)生更現(xiàn)實(shí)場景的感知。在下面的段落中混合的方法將更詳細(xì)地討論。在艾爾卡茲尼寶庫的左門在圖4和圖5中作為示范進(jìn)行處理。圖5.網(wǎng)狀模型左門3.1、數(shù)據(jù)配準(zhǔn)在注冊激光掃描儀和圖像數(shù)據(jù)過程的質(zhì)量,追求綜合處理是一個(gè)關(guān)鍵因素。這個(gè)注冊對(duì)應(yīng)坐標(biāo)可是否以在這兩個(gè)系統(tǒng)實(shí)現(xiàn)。由于對(duì)應(yīng)點(diǎn)的準(zhǔn)確的檢測和測量是很困難的，特別是對(duì)從激光掃描點(diǎn)云，直線在圖像和激光數(shù)據(jù)之間對(duì)應(yīng)元素之間測量

13、。這些線是按科林乃克和弗里奇，2003一個(gè)形狀匹配后跟一個(gè)修改的空間后方交會(huì)。該算法將三維直線從激光數(shù)據(jù)和相應(yīng)的二維圖像直線提取出來，這是由兩個(gè)已知點(diǎn)，成為一個(gè)參數(shù)化的表示。然后通過空間后方交會(huì)確定圖像的未知的外部參數(shù)。為了解決空間后方交會(huì)問題，利用高斯馬爾可夫模型的外方位參數(shù)的初始值的最小二乘算法的實(shí)現(xiàn)。他的從激光掃描儀數(shù)據(jù)的直線邊緣提取被簡化，如果必要的線是由兩個(gè)相交平面的表面定義，如它在圖6中顯示所示。數(shù)字圖像中的相應(yīng)的邊緣提取可以交互地或半自動(dòng)的基于邊緣的分割。至少三個(gè)相應(yīng)的直線都需要獲得一個(gè)獨(dú)特的空間后方交會(huì)解決方案的。3.2、距離圖像的生成后視坐標(biāo)和取向參數(shù)被記錄在激光掃描儀坐標(biāo)系

14、中，共線條件方程用來生成一個(gè)基于現(xiàn)有的點(diǎn)云的距離圖像在我們的示例場景中，點(diǎn)云是從1厘米平均分辨率鄰近視點(diǎn)收集。與相應(yīng)的圖像（1536x2304像素）的像素生成數(shù)目相同的距離圖像。 圖6.兩個(gè)相交的平面表面，其中之一是由網(wǎng)格線用于演示目的而表示 圖7。投影在對(duì)應(yīng)的圖像的左門的距離圖像。 艾爾卡茲尼寶庫門左邊,三個(gè)距離圖像生成的三張圖片是從不同的相機(jī)生成的。圖7描述了其中一個(gè)距離圖像投影相應(yīng)的影象。圖8。提取艾爾卡茲尼寶庫左側(cè)門的三維特征，基于圖像測量柱的內(nèi)緣。3.3、圖像分割分割過程用于從三個(gè)不同的數(shù)字圖像自動(dòng)提取線性特征的二維坐標(biāo)。用于此目的的基礎(chǔ)上，蘭瑟濾波器的邊緣檢測已經(jīng)應(yīng)用在3成像的圖像

15、。分段輪廓的第三個(gè)維度是從距離圖像提供。圖8中，出示了提取的艾爾卡茲尼寶庫的左側(cè)門的最終三維特征?？梢钥闯觯摂?shù)據(jù)包含了所有的邊緣和線性表面特征一個(gè)清晰輪廓?？偣不谔卣鞯拇硇园?43600個(gè)點(diǎn)，而原始點(diǎn)云的相同部分有11個(gè)萬點(diǎn)。3.4、基于圖像的測量阻擋的特點(diǎn)從顯示的三維功能可以看到在圖5中,由于激光掃描儀的位置,內(nèi)邊緣的門的右列沒有數(shù)據(jù)。該遮擋邊緣可以基于數(shù)字圖像的半自動(dòng)評(píng)估被添加到對(duì)現(xiàn)場一個(gè)完整的數(shù)據(jù)集。在我們的方法中，初始點(diǎn)的三維坐標(biāo)是手動(dòng)提取。然后一個(gè)自動(dòng)立體匹配已用于緊密間隔的圖像，在邊緣上添加更多的點(diǎn)。對(duì)于邊緣的分割部分使用極線約束進(jìn)行匹配。該遮擋邊緣被添加到三維特征，如在圖

16、8的右側(cè)部分的顯示。4、總結(jié)和結(jié)論本文中描述的工作是作為一個(gè)正在進(jìn)行的項(xiàng)目的一部分，,旨在強(qiáng)調(diào)整合基于圖像測量的必要性和激光掃描儀技術(shù)以優(yōu)化幾何精度和視覺的三維數(shù)據(jù)獲取質(zhì)量歷史場景。在我們的方法中，分割過程作為提取邊緣和線狀地物信息的一個(gè)中間步驟，而這些細(xì)節(jié)的三維信息是從激光掃描儀提供的數(shù)據(jù)。由兩個(gè)數(shù)據(jù)源的組合，三維的形狀特征可以準(zhǔn)確地確定，從點(diǎn)云的解釋和嚙合使用可用的圖像改進(jìn)模型。最后，該方法適用于基于圖像特征提取半自動(dòng)化。這些功能可以被添加到激光掃描數(shù)據(jù)，以便產(chǎn)生完整的場景的一個(gè)更為現(xiàn)實(shí)的感知。5、 致謝 特別感謝約旦哈希姆大學(xué)和佩特拉地區(qū)管理局的數(shù)據(jù)收集過程中的支持。6、 參考文獻(xiàn)馬布斯

17、伯樂蒂森，A.，2002。三維掃描儀器。學(xué)會(huì)/協(xié)會(huì)國際研討會(huì)上掃描的文化遺產(chǎn)的記錄，科孚島，希臘，pp.9-12。戴波沃克，E,1996。從照片渲染架構(gòu)建模。博士論文，加州大學(xué)伯克利分校。埃爾 - 哈基姆，S.，貝爾丁，A.，皮卡德，M.，2002。使用多種技術(shù)的古跡詳細(xì)三維重建。學(xué)會(huì)/ 協(xié)會(huì)國際研討會(huì)掃描文化遺產(chǎn)錄音，科孚島，希臘，5864。格倫，A.，雷蒙蒂諾，F(xiàn).，張，L.，2002。阿富汗巴米揚(yáng)大佛的重建。國際攝影測量與遙感，檔案第三十四卷5部分，363-368頁，科孚島，希臘?？巳R恩科，D.，弗里奇，D.，2003。向行人導(dǎo)航與定位。在第七屆東南亞調(diào)查：構(gòu)造工程師協(xié)會(huì)03，香港11月

18、3-7日。附錄 外文原文INTEGRATION OF DIGITAL PHOTOGRAMMETRY AND LASER SCANNING FORHERITAGE DOCUMENTATIONYahya Alshawabkehw, Norbert HaalaInstitute for Photogrammetry (ifp), University of Stuttgart, Germany Geschwister-Scholl-Strasse 24D, D-70174 Stuttgart yahyashawifp. uni_stuttgart.deCommission V WG 4KEY WOR

19、DS: Cultural Heritage, Photogrammetry, Laser Scanner, Fusion, Linear surface features, Semi-automationABSTRACT:Within the paper the potential of combining terrestrial laser scanning and close range photogrammetry for the documentation of heritage sites is discussed. Besides improving the geometry of

20、 the model, the integration aims on supporting the visual quality of the linear features like edges and cracks in the historical scenes. Although the laser scanner gives very rich surface details, it does not provide sufficient data to construct outlines for all surface features of the scanned objec

21、t, evene though they are clearly defined in the reality. In our approach, information on edges and linear surface features is based on the analysis of the images. For this purpose an integrated segmentation process based on image data will support the extraction of object geometry information from t

22、he laser data. The approach applies image based semi-automated techniques in order to bridge gaps in the laser scanner data and add new details, which are required to build more realistic perception of the scene volume. The investigations and implementation of the experiments are based on data from

23、Al-Khasneh, a well-known monument in Petra, Jordan.1. INTRODUCTIONThe generation of 3D models of historical buildings is frequently required during the documentation of heritage sitesi. e. for tourism purposes or to provide education resources for students and researchers. During the generation of t

24、hese models, requirements such as high geometric accuracy, availability of all details, efficiency in the model size and photo realism have to be met by the different approaches used for data collection EL- Hakim et al 2002. One well-accepted technique frequently applied in the context of heritage s

25、ite documentation is close range photogrammetry Gruen et al 2002, and Debevec 1996. In the past decade, these traditional terrestrial approaches have also benefited from the fact that digital image collection is now feasible with of-the-shelf cameras. Thus the efficiency of photogrammetric data coll

26、ection could be improved considerably by the integration of semi-automatic tools based on digital image processing. Additionally, laser scanning has become a standard tool for 3D data collection for the generation of high quality 3D models of cultural heritage sites and historical buildings Boehler

27、and Marbs 2002. These systems allow for the fast and reliable generation of millions of 3D points based on the run-time of reflected light pulses. This results in a very effective and dense measurement of surface geometry. Current limitations regarding the measurement rates, accuracy, or spatial poi

28、nt density will further disappear in the near future, thus laser scanning seems to become the dominating approach for the generation of 3D documentations and presentations of heritage sites.Despite the considerable progress of these approaches, there are still some limitations, which have an effect

29、on the quality of the final 3D model. Even though current laser scanners can produce large point clouds fast and reliably, the resolution of this data can still be insufficient, especially if edges and linear surface features have to be collected. In the contrary, the digital photogrammetry is more

30、accurate in outline rendition, especially if they are clearly defined in the reality. On the other hand, image based modeling alone is difficult or even impractical for parts of surfaces, which contain irregular and unmarked geometrics details. Additionally, the identification of points to be measur

31、ed, being manual or semi automatic, requires a long and tedious work, especially if a considerable number of points has to be captured.The complete coverage of spatially complex objects like heritage sites can only be guaranteed, if data collection is realized from different viewpoints. Even though

32、this is possible in most scenarios, problems can result from the fact that setting up and dismounting the complete laser system is relatively time consuming. In contrast to that, the effort to collect additional images with a standard digital camera can almost be neglected. Additionally, compared to

33、 laser scanning there are fewer restrictions on the range of measurements during image collection, which simplifies the selection of different viewpoint in order to cover the complete structure of the object. For this reason, it can be advantageous to complete a geometric model, which has been gener

34、ated from the laser measurement, based on intensity images captured independently from the range data. By these means object geometry, which is not available in the range data due to occlusions is provided based on photogrammetric measurements.Thus, the highest possible degree in efficiency and flex

35、ibility of data collection will be possible, if both techniques are combined during data processing. In our approach this integration helps to improve the geometry and visual quality of the collected 3D model. During data collection the information on edges and linear surface features like cracks is

36、 based on the analysis of the images, whereas information on object geometry is provided from the laser data. Additionally, areas, which are not accessible in the laser scanner data due to occlusions are added based on semiautomatic evaluation of the imagery. By these means, a complete 3D features f

37、or the scene can be generated with sufficient and clear details.Within the paper the presented approaches are demonstrated in the framework of a project aiming at the generation of a 3D vir-tual model of the Al-Khasneh, a well-known monument in Petra, Jordan. In section 2 the collection and pre-proc

38、essing of the relevant image and LIDAR data is discussed. This pre-processing is mainly required in order to coregister laser and image data for further processing. Section 3 exemplarily pre-sents our feature extraction approach using the hybrid system for the left door of Al-Khasneh.2 DATA COLLECTI

39、ON AND PREPROCESSINGThe collection of the data, which has been used for our investigations, was performed in cooperation with the Hashemite University of Jordan. One of the project goals is the generation of a 3D documentation of the Al-Khasneh monument in Petra city, Jordan, which is depicted in Fi

40、gure 1.Figure 1. Al-Khasneh facade, Petra 2.1 Al-Khasneh MonumentThe ancient Nabataean city of Petra has often been called the eighth wonder of the ancient world. Petra city in southwestern Jordan prospered as the capital of the Nabataean empire from 400 B.C. to A.D. 106. Petras temples, tombs, thea

41、ters and other buildings are scattered over 400 square miles, these architectures are carved into rose-colored sandstone cliffs. After a visitor enters Petra via Al-Siq, a two-kilometer impressive crack in the mountain, the first facade to be seen is Al-Khasneh, which is considered as the best-known

42、 monuments in Petra city. The Al-Khasneh facade is 40m high and remarkably well preserved, probably because the confined space in which it was built has protected it from the effects of erosion. The name Al- Khasneh, as the Arabs call it, means treasury or tax house for passing camel caravans, while

43、 others have proposed that the Al- Khasneh Monument was a tomb. Behind the impressive facade of Al-Khasneh, large square rooms have been carved out of the rock Sedlaczek, 2000.2.2 Sensors AppliedFor point collection, the 3D laser scanning system GS100, manufactured by Mensi S.A., France was applied.

44、 The scanner features a field of view of 360?in the horizontal and 60?in the vertical direction, enabling the collection of full panoramic views. The distance measurement is realized by the time of flight measurement principle based on a green laser at 532 nm. The scanning range of the system allows

45、 distance measurements between 2 and 100 meters. The scanner抯 spot size is 3 mm at a distance of 50 meters; the standard deviation of the distance measurement is 6 mm for a single shot. The system is able to measure 5000 points per second. During data collection a calibrated video snapshot of 768x57

46、6 pixel resolution is additionally captured, which is automatically mapped to the corresponding point measurements.In addition to the laser data, digital images were captured for photogrammetric processing using a Fuji S1 Pro camera, which provides a resolution of 1536x2034 pixel with a focal length

47、 of 20 mm.2.3 Measurement ConfigurationBecause it is not possible to have a complete 3D coverage for the Al-Khasneh facade based on data collected from a single station, three different viewpoints with five scans were done to resolve the occlusions. The problem to choose the viewpoint positions repr

48、esents an important phase of the survey for such a monument since potential sensor stations are restricted by the mountainous environment surrounding Al-Khasneh. Three positions were selected, from the entrance area of the monument, from the left of the monument, and one scan was collected from an e

49、levated viewpoint. Since the vertical field of view of the laser scanner from these positions could not cover all the facade from one scan, the left and top scanning were done using 2 scans from the same position, taking into consideration sufficient overlapping regions to allow for a subsequent int

50、egration. In total, the five scans resulted in almost 5 million collected points.All the acquired 3D models have been processed using Innovmetric Software, PolyWorks. The model of Al-Khasneh facade resulted from merging the five scans in an independent coordinate system into an absolute coordinate s

51、ystem. After registration of the scans using corresponding points, the software constructs a non-redundant surface representation, where each part of the measured object is only described once. The result of the combination of the five laser scans is given inFigure 2. The produced model has an avera

52、ge resolution of 2 cm with more than 10 million triangles.Figure 2. 3D Model of Al-Khasneh created from 5 scansIn additional to the outer survey, a 360-degree scanning from a station in the interior of the Al-Khasneh had been taken, which resulted in 19 million points. Figure 3 shows the point cloud

53、 of this scan with colour information overlaid.Figure 3. 360 degree scanning for the inner part of Al-Khasneh3 INTEGRATED DATA PROCESSINGAlthough the 3D model produced by laser scanner contains a large number of triangles, which are representing the surfaces, it can still difficult to recognize and

54、localize the outlines of the surface features. An example for this type of features, which are clearly visible in an image is depicted in figure 4. This data was collected from the left door of Al-Khasneh. As it can be seen from the corresponding 3D meshed model shown in figure 5, these cracks and t

55、he edges outlines are lost beyond the resolu-tion in the available laser data.Figure 4. The left door of Al-KhasnehIn order to support the visual quality of such details, a hybrid approach combining data from the laser scanner and the digital imagery was developed. For integration all data sets have

56、 to be coregistered in the first processing step. This is realized by aligning the extracted edges from both data sources using an al-gorithm developed by Klinec and Fritsch, 2003. After position and orientation parameters are computed for the sensor stations, distance images are generated from the

57、point cloud in order to provide the missing third dimension in the available images. Fi-nally, an integrated segmentation process based on the image data is be used in order to support the extraction of the details and the surface features outlines from distance images. Addi-tionally, the approach a

58、pplies a semi-automated feature extrac-tion from images to bridge gaps in the laser scanner data. By these means details can be added that are necessary for generat-ing more realistic perceptions of the scene volume. In the fol-lowing paragraphs the hybrid approach will be discussed in more details. The left door of the Al-Khasneh depicted in figure 4 and 5 is exemplarily processed.3.1 Data CoregistrationFigure 5. Meshed model for the left door 3.1 Data CoregistrationFigure 6. Two intersecting planar surfaces, one of them is represente