近景攝影測量相關資料外文翻譯

1、畢業(yè)設計（論文）外文翻譯題 目 photomodeler scanner在 古建筑測繪中的應用 專 業(yè) 測 繪 工 程 班 級 0901 班 學 生 指導老師 重慶交通大學2013年火山學通報，2009年7月，69卷1期，p105-108基于活動熔巖流可見光和熱感影像的傾斜攝影測量mike r. james. stuart robson. harry pinkerton. matthew ball手持相機數(shù)碼圖像越來越多地被用于科學目的，特別是在非接觸式測量是必需的地方。然而，他們往往由顯著的相機到對象的深度的變化和閉塞的斜視組成，復雜化定量分析。在這里，我們報告通過斜攝影技術來確定基于地面的

2、熱感照相機方位（位置并指出方向），并產(chǎn)生在西西里島火山的熔巖流場景信息。從基于大眾使用的消費級單反數(shù)碼相機的多個圖像來構造一個基于地面熱圖像的地形模型和參考。我們展示在2004-2005年火山爆發(fā)期間收集的數(shù)據(jù)和對于基于像素的熱感圖像，使用派生曲面模型來查看距離改正（考慮大氣衰減）。對于查看約為100至400米的距離，更正導致在輻射強度系統(tǒng)的變化就值方面高達3，其是假設在一個統(tǒng)一的平均圖像的觀看距離計算而得。關鍵詞：近景攝影測量，埃特納（etna）火山，熔巖流，熱感圖像引言：為了提高我們了解了熔巖如何流動并最終停止，需要更先進的測量（熔巖）流動的發(fā)生和冷卻的技術技術（hidaka，等。2005

3、年）。衛(wèi)星數(shù)據(jù)經(jīng)常用于監(jiān)測活火山，但為獲取準確的溫度信息，可行的空間分辨率為30 m左右的中紅外或近紅外區(qū)域（陸地衛(wèi)星tm和aster數(shù)據(jù)）或更大的熱紅外波段（60m的陸地衛(wèi)星etm +和aster的90米; donegan和flynn 2004; pieri 和 abrams 2004）。這些尺寸都大大高于在熔巖流表面熱性結構的空間變異，限制冷卻模型從而限制衛(wèi)星數(shù)據(jù)的使用。最近手持式熱成像儀的使用提供了一個潛在的解決方案，即通過實現(xiàn)1-103m的距離觀看，增加空間分辨率達到的一因子（1毫米左右）。因此，手持式熱成像儀獲取的圖像有潛力提供了豐富的（熔巖）流動模型信息，并提供地面實況信息用于衛(wèi)星

4、數(shù)據(jù)的解釋（例如calvari等。2005年）。不過，關鍵的缺點，存在于大多數(shù)近距離數(shù)據(jù)集（強烈的斜視角，未知的成像幾何關系與傳感器的空間位置）通常阻礙地理參考和目前制約定量分析。數(shù)字攝影測量技術的應用在火山已普遍局限于從傳統(tǒng)的航空圖像生產(chǎn)數(shù)字高程模型（dem）（baldi等，2000；kerle，2002年），或最近，從衛(wèi)星數(shù)據(jù)（stevens等人；2004年）。在一個較小尺度范圍，近景攝影測量和傾斜攝影已成功用于地貌研究（例如：chandler和brunsden 1995；lane等，2001年）和計算機視覺的方法已被最近開發(fā)從序列傾斜圖像測定火山地形（cache等，2003）。在這里，我

5、們將展示為了克服在使用傾斜角度和比較低分辨率的溫度傳感器時數(shù)據(jù)處理的一些固有問題，近景數(shù)字攝影測量技術是如何可以被用來聯(lián)合從任意位置熱和可見光相機獲取的圖像數(shù)據(jù)。自動攝影和圖像匹配技術（papadaki 2002年），可獲取地形數(shù)據(jù)，以及整頓和地理參考可見光與紅外線圖像。觀察對象的表面和相機方位的測定允許對熱圖像的每個像素的有關大氣衰減因素計算。我們利用在埃特納火山活動的熔巖渠道和流動陣地地面圖像來說明這些技術的應用。圖1地理位置埃特納火山和山谷德爾波夫。2004-2005年熔巖最終流域顯示為主圖上的黑色區(qū)域以及它們在2004年9月27號的流域顯示在插圖上。流動前端周圍的星號展示了攝影測量控制

6、的一些目標使用的位置。數(shù)據(jù)采集埃特納火山，在意大利西西里島，擁有最近既熱情洋溢又適度爆炸活動的歷史。經(jīng)過約一個相對平靜的一年，2004年9月7日，一小熔巖噴口開幕海拔2800米，在東南基地火山口。一周之內，在巴耶德爾波夫頂部兩個海拔相對較低的噴口下低落（在2650和2250米，圖1）也形成，熔巖向東流入山谷。在相對溫和的流動速率（大約3立方米每秒;伯頓等2005年），提供通道流量被冷受限（guest等。1987年），并且（在實地調查期間）小于2.5公里長，在monte centenari南部，谷底斜坡的裂隙有主動流動前端（圖2a）。同時有相當一部分發(fā)展在陡峭的地形流場有落石的危險，流動前端相對

7、可行。因此，地面的圖像可以獲取流動前端和遠端通道地區(qū)，在這個文章中使用的數(shù)據(jù)收集于9月27日2004。熱感圖像通過前視紅外thermacam s40獲得，它提供24的廣角（類似于一個具有aps尺寸傳感器的數(shù)碼單反相機50mm鏡頭）。該傳感器是一個320 240非制冷微測焦平面陣列，擁有7.5-13微米的光譜范圍。該熱感相機的幾何成像校準是很有必要的，因此擁有熱感標記的目標是必需的。因此，雖然初步校準已進行了成像幾何模型的改進（更正是由一階徑向畸變?yōu)橹鳎?，由于場地調焦的變化尚未被充分的考慮。etna火山的攝影測量技術需要每張圖像至少四個已知三維坐標用以觀察，以便可靠地估計攝影機方位。由金屬箔構建

8、的人工控制目標被部署在該區(qū)域;一些大的平面目標（約50cm）由一些小的（約5cm）“球”型目標構成，以增強短距離觀測精度。目標位置測定協(xié)調使用全球定位系統(tǒng)（gps）（promark x），對于比較接近的目標，目標間目標的距離可用卷尺測定。這些測量做為觀測值在攝影測量網(wǎng)平差與gps觀測數(shù)據(jù)一起解算。圖2 圖a和圖b分別為攝于2004年9月27日活動熔巖流的前端與渠道的可見光和熱感圖像，大約北向。對于規(guī)模，活躍流通的前面大約35米寬。可見光圖像顯示了一個不活動的流動前端，和在一個活動前端右前方部分枯竭的渠道（其在前一天很活躍）。熱感圖像上覆有一個從可見光圖像提取的三角曲面模型透明的視角。攝影測量和

9、結果攝影測量軟件的使用（vms系統(tǒng)，robson and shortis，）提供了一般實例的解決方案，適合有重疊的傾斜圖像帶的使用。每個可識別的控制好目標影像的量測使用三維坐標數(shù)據(jù)，為每副影像提供相機的起初方位值。這些最初值根據(jù)最小二乘法重新定義。如果需要（如地形數(shù)據(jù)生成），在區(qū)域網(wǎng)或光束平差（granshaw1980）進行之前，其他同源點可以生成以增加了測量網(wǎng)密度。校正的熱感圖像可以實現(xiàn)，可以通過兩種途徑，要么使用這種以熱識別目標為基礎的攝影測量方法，或攝影機的位置可以從在相同位置確定的影像確定，只需計算相機相關的旋轉角度。攝影測量數(shù)據(jù)后處理是利用matlab進行的。一個相對比較粗糙的數(shù)字高

10、程模型是通過地形數(shù)據(jù)點內插一個4m的三角網(wǎng)獲得的。通過一個合適的投影變換表面可覆到熱成像（圖2b）。表面的任何部分的昏暗情況是通過三角形的深度規(guī)律并考慮最鄰近的“可見”三角形逐像素的觀察處理的。在圖 2b中，用相機采集的溫度數(shù)據(jù)集 0-500 c的范圍被展示?，F(xiàn)場觀看的距離約在50至400米，流動前端距相機大約110米。為了對溫度數(shù)據(jù)的定量分析，由于水汽吸收對大氣衰減的影響應加以考慮。對每個像素的衰減程度與大氣的相對濕度與大氣的相對路徑長度有關。每個像素所需要的觀測距離 是從觀察的地形三角形與射線額交點計算出來的。雖然外部大氣校正程序（伯克等人，1989）也可以用，在這里每個像素修正是通過與其

11、相類似的代碼的flir的thermacam研究員的分析軟件實現(xiàn)的。為了避免因混合像元效應（羅里等人，1988）的復雜性，在后續(xù)分析之前，溫度值轉換為發(fā)射功率（出射度，輻射的波長為7.5和13微米之間）。而每像素修正幅度可以被獲得，通過比較那些“平均”距離在200以上貫穿整幅圖像的計算。計算出的功率值之間的誤差均大于 3%（對于遠處的物體出射度增加和對于近處的物體出射率減少）相對于整個糾正影像（測得的75相對濕度）。與一個已知的表面結合，相機的方向和傳感器的成像幾何可以獲取熱感影像的正射影像和地理參考的數(shù)據(jù)。一個例子如圖3。說明如下，對于這幅影像，熔巖流的一些重要的區(qū)域被靠近相機的不規(guī)則地形流域

12、所阻隔。這能夠被避免通過使用較少的傾斜影像（如從直升機上獲取的數(shù)據(jù)）或結合從不同位置獲取的地面影像。一些曲解是很明顯的在正北方向的成像通道的最高區(qū)域，表面模型邊緣問題的矯正誤差由于傾斜視角變得更加復雜。雖然這些問題將在今后的工作中加以解決，流動特征在當前的矯正數(shù)據(jù)中可以很容易的鑒別。例如，使用高架出射度平行線理劃定通道的（相對于堤壩）活躍的地區(qū)，在觀看范圍約310米，西部通道的分支機構有17.5 m寬，它縮小到約9米，由于流動越過了一段約260m的斜坡區(qū)域（圖3）。與此相比，平均通道寬度17m和最大最小寬度分別為37m和2m，從較早前噴發(fā)收集的激光測高數(shù)據(jù)測定的（mazzarini等，2005

13、）。根據(jù)這通道部分，根據(jù)中部地區(qū)流量測量的出射度約為700-1700，（對應于黑體溫度200-290）和在流域邊緣高達4850（對應于約575 c黑色體溫）。 the thermacam s40 的0-500 c溫度范圍（這個圖片使用）對于明顯大于580 c的溫度給予飽和值。在此圖像上，39個像素是飽和的，并且除少數(shù)幾個例外，這些都是靠近相機觀測的流動前端。然而，他們代表小于0.3%的影像前端和相似的影像，使用500-1,500 c的溫度范圍獲取的，展示了這一視覺領域最高的明顯氣溫約為700 c。這一區(qū)域在流動前端的后面，（在視線距離約110m到200m，圖3）展示了最低出射度值約為350 （

14、或約為80 c）。在這一地區(qū)，視角是極其傾斜的，并且這一沒有形成流動通道的區(qū)域在淺斜坡正在減速，沒有揭露熱的和新材料。圖3正射熱圖像。每個像素值已被糾正了觀測距離的有關大氣衰減（環(huán)境溫度，9.1，相對濕度75）。軸尺度單位為米，相對于攝像機的位置。由于相機方位的影響，被遮蔽的區(qū)域表面被標記為黑色。角度測量的本質是一種定義其范圍使用的三角測量結果的表面模型。這里提出的數(shù)據(jù)證明了成像的熔巖流近景攝影測量技術的潛力。（圖2b，3）所示的熱感圖像表明，為了最大限度地成像流面積，至少有一個具有顯著上調或下調流方向的影像應該被獲得。這種觀點需要一個基于每個像素的視距改正，為了消除大氣吸收的影響，否則就會導

15、致在估計冷卻趨勢上的系統(tǒng)誤差。相機的相對方位知識（相對于成像面）對研究觀測角度及明顯溫度的解決方案的影像有著至關重要的作用。此外，這種圖像的校正，可以在一個相對高的重疊率下獲得，將提供圖像序列，比較適合流動通道的活動和演化，積液率估計和流場的范圍，呈現(xiàn)有價值的資源與其他數(shù)據(jù)集的集成以及危害映射?？偨Y： 1. 多片近景攝影測量技術已被成功地應用于熔巖流，通過店地面相機獲得的可見光的和熱感影像。2. 可見光影像被用來生成地形數(shù)據(jù)，并協(xié)助該熱感影像的校正。3. 已知成像幾何和地形數(shù)據(jù)的組合可以使觀察距離得以計算，并且相關的大氣衰減修正可以應用于熱感圖像上的每個像素。4. 正射影像和具有地理參照的熱感

16、圖像為熔巖流的發(fā)展（如渠道移徙，從渠道向管狀地形的轉變，制約前進流速方面的影響）并與其他數(shù)據(jù)集的結合。致謝：這項工作得到了英國皇家學會的支持。我們感謝 s. calvari, j. dehn, d. rothery 和 一個匿名評論家對于已改善的文本徹底審查。參考文獻baldi p, bonvalot s, briole p, marsella m (2000) digital photogrammetry and kinematic gps applied to the monitoring of vulcano island, aeolian arc, italy. geophys j i

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28、e photogrammetry with visible and thermal images of active lava flowsmike r. james. stuart robson.harry pinkerton. matthew ballabstract digital images from hand-held cameras are increasingly being acquired for scientific purposes, particularly where non-contact measurement is required. however,they

29、frequently consist of oblique views with significant camera-to-object depth variations and occlusions that complicate quantitative analyses. here, we report the use of oblique photogrammetric techniques to determine ground-based thermal camera orientations (position and pointing direction), and to g

30、enerate scene information for lava flows at mount etna, sicily. multiple images from a consumer grade digital slr camera are used to construct a topographic model and reference associated ground-based thermal imagery. we present data collected during the 20042005 eruption and use the derived surface

31、 model to apply viewing distance corrections (to account for atmospheric attenuation) to the thermal images on a pixel-by-pixel basis. for viewing distances of 100 to 400 m, the corrections result in systematic changes in emissive power of up to 3% with respect to values calculated assuming a unifor

32、m average viewing distance across an image.keywords close-range photogrammetry. etna volcano.lava flows.thermal imagingintroductionin order to improve our understanding of how lavas flow and eventually stop, improved measurements of flow evolution and cooling are required (hidaka et al. 2005).satell

33、ite data are regularly used for monitoring activevolcanoes, but the spatial resolutions available for obtaining appropriate temperature information are currently 30 m in the mid- or near-infrared region (landsat tm and aster data) or greater in the thermal infrared region (60 m for landsat etm+ and

34、90 m for aster; donegan and flynn 2004; pieri and abrams 2004). these dimensions are considerably larger than the spatial variability in thermal structure of lava flow surfaces and thus limit the use of satellite data for constraining cooling models. the recent availability of hand-held thermal imag

35、ers offers a potential solution by enabling viewing over distances of order m, increasing spatial resolutions by up to a factor of (to 1 mm). thus, images acquired by handheld instruments have the potential to provide a wealth of information for flow models and also provide ground-truth information

36、for the interpretation of satellite data (e.g. calvari et al. 2005). however, the critical disadvantages which exist in most close-range datasets (strongly oblique viewing angles, unknown imaging geometry and sensor positioning) usually prevent georeferencing and currently constrain quantitative ana

37、lysis.the application of digital photogrammetry techniques within volcanology has been generally confined to producing digital elevation models (dems) from conventional aerial imagery (baldi et al. 2000; kerle 2002) or, more recently, from satellite data (stevens et al. 2004). on a smaller scale, cl

38、ose-range and oblique photogrammetry has been successfully used for geomorphological research (e.g. chandler and brunsden 1995; lane et al. 2001) and a computer-vision based approach has been recently developed for determining volcano topography from sequences of oblique images (cecchi et al. 2003).

39、here, we show how close-range digital photogrammetric techniques can be used to combine image data acquired from arbitrarily positioned thermal and visible cameras in order to overcome some of the data processing problems inherent in using oblique viewpoints and comparatively low resolution thermal

40、sensors. automatic photogrammetric and image matching techniques (papadaki 2002) are employed to obtain topographic data, and to rectify and georeference visible and thermal images. determination of the observed surface and camera orientations allows the relevant atmospheric attenuation factor to be

41、 calculated for each pixel of the thermal images. we illustrate the application of these techniques using ground-based images of active lava channels and flow fronts on etna volcano.data acquisitionmount etna, in sicily, italy, has a recent history of both effusive and moderately explosive activity.

42、 after about a year of relative quiescence, on 7 september 2004, a small lava vent opened at 2,800 m a.s.l., at the base of the se crater. within a week, two lower vents at the head of the valle del bove (at 2,650 and 2,250 m, fig. 1) had also formed, from which lava flowed east into the valley. fed

43、 at relatively modest effusion rates (3 m3 s1; burton et al. 2005), the channel-fed flows were cooling limited (guest et al. 1987) and (during the period of fieldwork) were 2.5 km long, with active flow fronts at the break in slope on the valley floor, south of monte centenari (fig. 2a).whilst a con

44、siderable portion of the flow field developed on steep topography exposed to rock fall hazard, the flow fronts were relatively accessible. hence, ground based images could be acquired of the flow front and distal channel regions and the data used in this paper were collected on 27 september 2004.vis

45、ible images were acquired with a canon eos 300d (30722048 effective pixels) fitted with a fixed-focus 28 mm lens, the imaging geometry of which had been precalibrated in a laboratory (robson et al. 1999). thermal images were obtained with a flir thermacam s40 which provides a horizontal field of vie

46、w of 24 (similar to that of a 50-mm lens on a digital slr with an aps dimensioned sensor). the sensor is a 320240 uncooled microbolometer focal plane array, with a spectral range of 7.513 m. the imaging geometry of the thermal camera is non-trivial to calibrate, since targets with a thermal signatur

47、e are required. hence, although preliminary calibration has been carried out to refine the imaging geometry model (corrections are dominated by the first order radial distortion term), variations due to required on site focusing adjustments have not yet been fully accounted for.fig.1 geo graphical l

48、ocation of etna volcano and the valle del bove. the final extent of the 20042005 lavas is shown in black on the main map and their extent on 27 september 2004 is shown in the inset sketch. the asterisks surrounding the flow fronts demonstrate the positions of some of the photogrammetric control targ

49、ets used.the photogrammetric technique used on etna requires a minimum of four known three-dimensional target positions to be observable within each image in order to reliably estimate the camera orientation. artificial control targets constructed from metal foil were deployed in the field; some lar

50、ge (50 cm) flat targets were augmented by smaller (5 cm) ball targets to improve precision at short viewing distances. target positions were coordinated using gps (promark x) augmented, for relatively close targets, with target-to-target slope distances made using a tape measure. these measurements

51、were included as observations in the photogrammetric network adjustment along with the gps data.fig. 2 visible (a) and thermal (b) images of the active flow front and channels on 27 september 2004, looking approximately north. for scale, the active flow front is 35 m wide. the visible image shows an

52、 inactive flow front and partially drained channel (which had been active during the previous day) to the right of the active front. the thermal image is overlain with a perspective view of the triangulated surface model derived from the visible images.photogrammetry and resultsthe photogrammetric s

53、oftware employed (vms, robson and shortis, ) provides a general case geometric solution, suitable for application to networks of convergent oblique imagery. measurements of each identifiable control target image are used along with the three-dimensional target coordinate data, to provide camera orie

54、ntation starting values for each image. these initial values are then refined by least squares based resection. if required (e.g. to generate topographic data),additional homologous points can be generated in order to increase the density of the measurement network, before a network or bundle adjust

55、ment (granshaw 1980) is carried out. registration of the thermal images can be achieved either by using this target-based photogrammetric approach with thermally identifiable targets, or, where a camera position can be ascertained from a visible image taken at the same location, by calculation of re

56、lative camera rotation angles only.post-processing of the photogrammetric data was carried out using matlab. a relatively coarse dem was obtained by interpolating a 4-m triangulated mesh between the topographic data points acquired. under a suitable projective transformation, the surface can be over

57、lain onto the thermal imagery (fig. 2b). obscuration of any part of the surface is handled by depth-ordering the triangulation and considering the closest triangle viewed by each pixel to be the one observed.in fig. 2b, temperature data collected with the camera set to a scale of 0500c are shown. vi

58、ewing distances for the scene vary from 50 to 400 m and the flow front was 110 m from the camera. for quantitative analysis of the thermal data, the effects of atmospheric attenuation due to absorption by water vapor should be accounted for. the magnitude of the attenuation for each individual pixel is thus a function of both the relative humidity and the appropriate atmospheric path length. the per-pixel viewing distances required are calcula