Computer Vision in the Temples of Karnak : Past, Present & Future

The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Volume XLII-5/W1, 2017 GEOMATICS & RESTORATION – Conservation of Cultural Heritage in the Digital Era, 22–24 May 2017, Florence, Italy COMPUTER VISION IN THE TEMPLES OF KARNAK : PAST, PRESENT & FUTURE V. Tournadre a, Ch. Labarta b, *, P. Megard c, A. Garric d, E. Saubestre b, B. Durand b a Iconem, Paris, France – vincent.tournadre@iconem.com b CNRS, USR 3172 - CFEETK - LabEx Archimede - charlie_lbt@hotmail.com, emilie.saubestre@yahoo.com, benjamindurand@live.fr c CNRS, USR 3172 - CFEETK – MAEDI paul.megard@yahoo.com d CNRS, USR 3172 – CFEETK antoinegarric@yahoo.fr Commission WG V/1, WG V/2, WG II/8, WG VI/2 & CIPA KEY WORDS: archaeology, cultural heritage, digitization, 3D modeling, photogrammetry, Egypt ABSTRACT: CFEETK, the French-Egyptian Center for the Study of the Temples of Karnak, is celebrating this year the 50 th anniversary of its foundation. As a multicultural and transdisciplinary research center, it has always been a playground for testing emerging technologies applied to various fields. The raise of automatic computer vision algorithms is an interesting topic, as it allows non- experts to provide high value results. This article presents the evolution in measurement experiments in the past 50 years, and it describes how cameras are used today. Ultimately, it aims to set the trends of the upcoming projects and it discusses how image processing could contribute further to the study and the conservation of the cultural heritage. 1. INTRODUCTION It is interesting to note that the process of acquisition and the restitution involved teachers as well as students (Yoyotte, Mainly dedicated to the god Amun-Ra, Karnak had stubbornly 1966). Still used today as the base of the topographic canvas remained the heart of the religious and political power for and refined years after years (Azim et al., 1998), this map more than two millennia. It is among the best preserved sites proves how pedagogical programs can have an impact half a of Egypt. Since the end of the 19 th century, French century later. Egyptologists have been studying the group of monuments Starting in the mid 1980’s,(Vergnieux & Gondran, 1997; within the main precinct, which expands over an area of 2.6 Vergnieux, 1999) led a study using modern computer aided km2. These include the temple dedicated to Amun-Ra and design technologies focusing on 12 000 blocks from the reign several other structures attached to the cultic center. The site of Akhenaten, who is known as the heretical pharaoh. was built by the greatest kings of Egypt, among which are Senusret I, Thutmose III and Ramesses II, and it presents a rich 2.2 Twenty-first century collection of monuments whose diversity is a unique witness of the religious, political and technical changes. Karnak continues The technological revolution induced by the introduction of to be an object of research that is periodically enriched by computers has impacted photogrammetric processes with the archaeological discoveries. The latter are partially made emergence of digital photogrammetry. In the early 21 st century, possible thanks to technologies in constant evolution. the computer vision approaches brought a lot of automation in As of today, more and more bridges are built between the so- the processes, renewing the interest for 3D reconstructions called “hard and soft sciences”. This article aims to present from images. how collaborations between the Egyptologists and At the beginning of 2000’s, digital photogrammetry has started photogrammetry specialists help the ongoing work of to be employed, in combination with terrestrial laser scans in excavation and restoration, and to contribute to a better two digitization projects. This period constituted an understanding of the hieroglyphic inscriptions studied in the intermediate technological phase before its current Projet Karnak 1. independent use, low-cost and overall easier method. The first one aimed at studying the 134 columns standing 13 to 20 2. PAST meters high in the great Hypostyle Hall (Chandelier et al., 2009). A French-Canadian mission produced 3D models of the 2.1 Early experiments columns and derived unrolled orthophotographs. Another campaign is still undergoing and interdependent with the The 3D modelling of the environment has been a wide subject American-Canadian epigraphic mission conducted by J. Revez of interest in the 20 th century. The evolution of measurement and P. Brand (Meyer, 2004; Meyer et al., 2005; Brand et al., techniques has been an opportunity to create copies of our 2013). cultural heritage, which is still today a challenge for the The second important project of this decade took place in the preservation of endangered sites. temple dedicated to the goddess Opet and the god Osiris. Led In 1967, a few years after its participation in the conservation by E. Laroze, it aimed at producing a 3D model of the temple of the antique Nubia heritage, including the famous Abu thanks to the use of both LiDAR and digital photogrammetry Simbel temple, IGN - the French mapping agency – produced (Chazaly & Laroze, 2005). Among other uses, it was valuable the first thorough map of the Karnak temples at a 1:500 scale to produce orthophotographs and cross sections scaled at 1:50. from an aerial stereophotogrammetric acquisition. Between 2011 and 2014, the Center, always open to innovative technical approaches, hosted several survey by the University * Corresponding author This contribution has been peer-reviewed. doi:10.5194/isprs-archives-XLII-5-W1-357-2017 357  The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Volume XLII-5/W1, 2017 GEOMATICS & RESTORATION – Conservation of Cultural Heritage in the Digital Era, 22–24 May 2017, Florence, Italy of Oxford, which involved the use of Reflectance be postponed to the post-excavation work. This type of Transformation Imaging (RTI). (Frood & Howley, 2014) used document was difficult to produce until some years ago. Today, this technique for the study of ancient graffiti located in the export of these 3D models is made under PLY format, and various areas of the temple. This computational photographic they can be consulted with free and open-source software method is particularly apt to get clear images of shallow (CloudCompare, 2017). engravings and so to gain a better understanding of these non- When in 2015, a “favissa” was discovered next to the temple royal inscriptions. of Ptah (Charloux et al., forthcoming; Charloux & Thiers, 2017), digital photogrammetry was already employed as a 3. PRESENT common tool by CFEETK’s land surveyor. The experience accumulated in the previous years opened new possibilities; 3.1 Applications thanks to the expertise of K. Guadagnini, it was first time an animated video could be reconstructed from several After 50 years of progressive evolution and field testing, digital photogrammetric acquisitions. Apart from its scientific value, photogrammetry is now a relatively mature technology. It has the video proved an innovative and powerful tool to share the impacted – at various degrees – each profession gathered in the step-by-step discovery to the public. Center, from that of the land surveyor, to that of the stone Another application of the 3D model is the realization of mason, including the photographers, the archaeologists or the stratigraphical cross sections, from the accumulation of several Egyptologists. copies of ortho-images. In any location of the site, it is possible to define an axis of a few centimeters wide and obtain the 3.1.1 On the archaeological excavations: Since 2008, various stages of the excavation for such axis. If this one excavations are being carried on in the precinct of Ptah, in the followed the stratigraphy and if every stratum was ortho- northern area of Karnak. The main goal of the work is to set rectified, a cross section can be derived from the various the evolution of the enclosure walls, the better preserved layers. The results of this technique are convincing as they period being the Ptolemaic one. To gather topographic deliver the same level of accuracy that can be obtained informations of this brick-built Ptolemaic surrounding wall, the throughout the excavation on the field, which requires the first archaeologists to work in the area were using a total installation of a permanent axis chosen in advance. This station in order to create a minimalist pointcloud (a few exploitation of the 3D imaging avoids the time-consuming hundred points). Each of these dots were then printed on paper realization of cross section along the excavation as well as it and connected. The paper being then scanned and used as the offers a large freedom concerning the choice of its location. basis to draw the final map on Illustrator or AutoCAD. This method soon appeared to be very long and not very efficient to 3.1.2 On the epigraphic studies: One of the main goals of deal with the large mud bricks structure in the investigated the CFEETK is the study of epigraphic inscriptions. Traditional area. Having a very limited working schedule on the epigraphic survey is work that require patience, precision and excavation, a solution had to be found to improve the survey. flexibility. It sometimes requires to set up scaffolds, work in Meanwhile, photogrammetry has developed enough to study urgency, on extremely fragile surfaces, etc. such structures efficiently. Photography has always worked alongside of this scientific A few years later, it has become essential for archaeologists activity, but the quality of digital images remained and to speed up the process of field documentation. In unsatisfactory for many years, especially concerning comparison with the traditional method to maps of the applications of photogrammetry (Rosenberg, 1955, Gruen, excavated area, the image based approach appears to be much 1996). more effective in terms of time requirements, accuracy and completeness of the survey (introducing the possibility to produce new types of documents later on). Concretely, within the framework of the excavation of the temple of Ptah, a survey that previously required a full day of work on the field can now be achieved within an hour. The photogrammetric acquisition follows the recommendations of (Chandelier, 2011). A few Ground Control Points (GCP) are surveyed on the edges of the area of interest (with a relative accuracy of a few millimeters). A 4 meters pole and a remote control are used to get the most favourable viewpoints, and the shots are treated with Agisoft Photoscan. The ortho-images computed are likely the most important products for this specific mission, as they can be imported in a CAD software to draw the excavation map. Multiscale works can also be realised easily through this technique, as for example drawings of individual bricks that can be inserted directly in the georeferenced CAD file. By following this process several types of documents can be produced: 3D models (possibility to create videos), ortho-images, excavation maps, etc. The production of the archaeological documents has benefited from that technology, and so has their exploitation. The realization of a 3D model in a sector constitutes a digital copy of an incomparable precision/resolution, while remaining a very simple tool that can be used by non-experts of 3D modeling. For every point in a 3D model, one can measure its Figure 1: On the left, general view of the inscriptions to study height from the ground, or compute its distance from another (inside the blue frame). On the right, result of the image point. This exploitation of the 3D imaging also allows to save stitching after orthorectification time during the field work, as some of the measurements can This contribution has been peer-reviewed. doi:10.5194/isprs-archives-XLII-5-W1-357-2017 358  The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Volume XLII-5/W1, 2017 GEOMATICS & RESTORATION – Conservation of Cultural Heritage in the Digital Era, 22–24 May 2017, Florence, Italy With the recent full frame cameras and their very large sensor recorded in the archive through photographies, the lack of size and resolution (Nikon D810 with 36.15 megapixels as an reliable 3D informations can be restrictive, for example when example), the equipment is faster and more efficient to provide the elements are considered in a reconstruction hypothesis. good quality images to the scientists. Furthermore, the In addition to the traditional photographic archive, a production of orthophotographs became a new way of image photogrammetric acquisition is realised on the best pieces. As a making, as many close-range pictures can be compiled into a 360° acquisition is generally possible, the use of GCP is not single one, in which the optical distortions and the perspective necessary as such acquisition geometry does not lead -in the defaults can be estimated and corrected. authors experiences- to problematic drift errors. A calibration Traditional tracing techniques, that imply transparent plastic card is used to resolve the unknown scale factor, which has sheets fixed directly onto the stone surface, have been used for proven to be cost-effective as well as efficient for the usages decades to produce facsimile. The technique has proven considered. A short video presenting the object can then be effective to copy hieroglyphic inscriptions, but it raises a few produced, this is a powerful means to share discoveries that problems. The most striking drawback of this technique is that could otherwise remain hidden for years. Ortho-images can it requires to stay on the field during the whole study. A first also be realized to have different views of the object. drawing is usually made on the plastic sheet, which is then As for the field documentation, the creation of a cross section photographed and digitized in a vector software. The drawing on an object from its 3D model is an interesting application. is then printed on paper, and verified on the field against the The tools included in Agisoft Photoscan are helpful to segment original. An image-based approach in which an an object and to export an ortho-image of the remaining half orthophotograph is the base for the vector drawing presents (Figure 2). This application facilitates the drawing of responses to these issues. voluminous objects such as millstones, whose heavy weight are Some of the most immediate advantages are the possibility to not a problem any more as it is not necessary to manipulate produce images of very large structures, walls and blocks, with these. Meanwhile, the archaeologist is released from a tedious no distortion and with a result nearly as good as a traditional activity, he only intervenes in the realization of the epigraphic drawing. In addition, when the set-back distance is vectorization in the post-excavation. so short that the photographer cannot shoot a whole scene within a single frame, he can apply a photogrammetric acquisition protocol and produce a photomontage with higher quality and better precision than the photomerge tool on photoshop software. As an example, it is possible to make a photograph of an 4,5 meters high mast-grooves with only a 2 meters gap to take the photos (Figure 1). The process that the CFEETK employs to create orthophotographs is the same than in archaeology but it doesn’t require GCP, as the visual results are satisfying as they are for the epigraphic study. To solve the orthograph’s orientation unknowns without GCP, a couple of points can be indicated on the horizontal or vertical lines that are often present on the Egyptian scenes. This kind of process requires a high computing power so they can respect the studies deadlines. The VIIIth pylon has been the first massive monument in Karnak subject to a photogrammetric acquisition for its epigraphic study. 3500 pictures have been shot to cover one face of the structure (which would then require 14000 images for the whole monument). As a result of recent material investments, the chunk could calculated within a day (produced by K. Figure 2: Study of a millstone: 1- Textured 3D model; 2- Ortho- Guadagnini & P. Soubias), while it took almost 3 days with image (top view); 3- 3D model segmented; 4- Cross section older material. Moreover, the final ortho-image can be very drawn from the segmented 3D model heavy as a very fine resolution is mandatory for the hieroglyphic study: about 18GB in that case. Such high 3.1.4 In the anastylosis works: For more than a century, resolution documents can be hard to open on a standard dozens of monuments have been rebuilt in Karnak Temple by working station, to work with or to upload. studying thousands of stones, coming from fallen structures or CFEETK's photographic department has been using excavations, participating thus in the conservation and the photogrammetry as a tool to overcome difficulties on the field enhancement of this unique site. and nowaydays the photographers’s work in the center is made A new reconstruction project has recently started: the of 20% of field work (single shot images, mainly for objects) reassembly of 250 blocks onto the Cachette Courtyard walls, and 80 % of office work (image treatment with Adobe built by Thutmose III and especially decorated by Ramesses II Photoshop and Agisoft Photoscan, e.g. walls and monuments). and Tutankhamun. Partially rebuilt following the study of (F. At the end of the process, these images are used as high Le Saout, 1982), this anastylosis is based on a research done definition reference image in the Projet Karnak which aims at by (G. Dembitz, to be published) who produced, from labelling the temples as a whole. The computing power is epigraphic survey and old photographs, some views of the surely the biggest challenge that one will have to overcome. reassembled stones. These studies were done to document the meaning of the decorated scenes and the hieroglyphic texts. 3.1.3 On the objects and statuary study: The Even if these documents are scaled, they aren't accurate enough excavations led in various parts of Karnak Temples have dug to take measurements on and be used on the field in the up hundreds of objects in the last years (statuettes, ceramic, reconstruction process, as they only indicate the relative millstones,…). Their study is sometimes complex as their positions of the decorated faces. fragility can necessitate to limit their access. Traditionally This contribution has been peer-reviewed. doi:10.5194/isprs-archives-XLII-5-W1-357-2017 359  The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Volume XLII-5/W1, 2017 GEOMATICS & RESTORATION – Conservation of Cultural Heritage in the Digital Era, 22–24 May 2017, Florence, Italy Figure 3: Tutankhamun scenes on east side of the Cachette Courtyard East Wall. Old photographs and ortho-images of all the blocks to be rebuilt have been scaled and accurately preassembled on CAD software (ongoing reconstruction hypothesis). One of the main difficulties of anastylosis, especially when the measurement of decor elements and joint positions, without monument is incomplete, is the first laid courses cannot be being overly cumbersome. readjusted during the laying of the next ones, and these not Unlike the epigraphic use-case, the visual information derived only have to connect with the part already assembled but also, from the image reconstruction are not as important as their in the end, with those of the existing building. Note that each geometric quality. On a 60m long and 8m high wall, about a stone weights about 2.5 tons. hundred images were taken from 3m (Nikon D90). To The reassembly of all the blocks to their original position on guarantee this geometric quality, 6 to 10 GCP are set on the the structures still in place requires a millimetric accuracy. wall, associated with close-up pictures indicating their Each one needs to be carefully surveyed with these positions (defined on easily identifiable elements such as the specifications to know the dimensions and the precise end of a line of decoration, the tip of a particular crack, etc.). A architectural characteristics as to the course heights, block 3D model is created, allowing to compute orthophotographs on lengths, and distance between the decorative elements and the vertical side. Inserted into a CAD software, the next step is joints. to integrate all the blocks into the complete orthophotograph of As explained above, traditional survey techniques are long and the wall. Two solutions are possible: tedious (in this case, it would require scaffolding, plumb level, - Using historical images if the quality is good enough, drawing board, etc.), while an image-based approach is an although this may not be the best solution. opportunity to accelerate this process. - Making orthophotographs of each block (limited to 5/6 shots) Therefore, orthophotographs on both sides of each wall have In both cases, the distance between two details on each been made with a resolution adapted to the direct needs of the decorated face are measured, and thus all blocks can easily be reconstruction work: sufficient enough to record all necessary imported and scaled in the CAD file. (Figure 3) information, allowing the reading of hieroglyphs, the Therefore, it is no longer necessary to make measurements either on the wall or on the blocks as the measurements are all Figure 4: Assembly test scaled on the 12m high wall top part with orthophotographs of recently discovered blocks (Cachette Courtyard North Wall, ongoing reconstruction hypothesis). This contribution has been peer-reviewed. doi:10.5194/isprs-archives-XLII-5-W1-357-2017 360  The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Volume XLII-5/W1, 2017 GEOMATICS & RESTORATION – Conservation of Cultural Heritage in the Digital Era, 22–24 May 2017, Florence, Italy easily accessible in the ortho-image CAD file: widths of the scanning the block within half an hour. In total, 397 images different scenes, height of the text lines, distance between a were taken on the 60 by 70 cm face. line and a joint, etc. all within millimetric accuracy. Although it is very well known that zoom lenses with unstable With this kind of information, the reconstruction work can mechanical parts do not offer the best geometric stability of the easily be done "virtually" and then on the field. For the North calibration (Remondino & Fraser, 2006), the automatic post Wall top part (Figure 4), which is 12m high and difficult to production work was completed within a few hours, providing survey, the position of 16 recently discovered blocks has been an overview of the entire block (Figure 6). The results confirmed by using this photogrammetric process without even achieved both in terms of time requirement and visual quality moving them, which is rather practical because some stones are satisfactory. Another way to get these results would have weigh more than 4 tons. been to move the massive stone, which is for obvious reasons Computer vision applications are also possible in other more complicated. Although, if the general view of the block is reconstruction projects: on the Thutmose III bark shrine acceptable for the epigraphic study, its quality is way beyond anastylosis (achieved in September 2016), a huge broken the one produced in proper conditions, which is probably due monolithic ceiling slab had to be moved and reinstalled on the to the lack of good lighting source and to the low-cost camera chapel's top. After 3D modeling each of the fragments, Cloud that was used (16MP CMOS sensor, with a mediocre optical Compare was used to know accurately (to cubic centimeter) Zoom-NIKKOR glass lens 28-140mm that made achromatic their volumes, which would have been hard with traditional aberrations and the compressed jpg files as the only option on approaches as the objects shape were not rectilinear. Knowing this camera). the density of the calcite, the slab mass was estimated at It is still interesting to note that the first photographic 76.2 tons. Having to lift it manually onto the 4.5m high chapel acquisition resulted in an incomplete orthophotograph. The (with hydraulic jacks and temporary walls), it was very useful lack of a sufficient overlapping pictures produced a couple of to first know its mass precisely. In addition, by daily shots, a holes, which have been completed through additional shots. time lapse video has been realized of the complete lifting operation to highlight the anastylosis and his its presentation to the public (https://youtu.be/8D2Fl8A3rIY). Figure 5: General view of a block difficult to access Figure 6: Screenshot of the textured model and camera poses. The lower right part has been completed through an additional 3.2 Recent experiments acquisition The multidisciplinary team has now been experimenting 3D 3.2.2 On the use of depth maps: To improve the full reconstruction from images for years. Then a new look can be understanding of the Karnak Temple, the epigraphic study of given on problems that were though unsolvable – or really hard the numerous engraved inscriptions is essential. The site is to overcome. Three recent and original applications are being sprinkled with historical or religious inscription on various explored. substrates : architectural elements, furniture, statues, etc. Their conservation state are sometimes really good, while others are 3.2.1 On the use of small cameras: It is very common to highly deteriorated, in which case it is complicated to read or find re-employed epigraphic blocks in the foundations of an even distinguish the signs carved on the stones. It is especially edifice. The sanctuary of Ermant-Hermonthis, on the west side true when their surface have eroded or when the inscriptions of Luxor, is a good example of this practice. Many blocks from have been hammered. When working from pictures, the texture the 18th Dynasty have been used to build the foundations of the of the stone, the shootings conditions or even the location of temple from the Ptolemaic and Roman period. the block can have a negative effect on the study. The method Although the epigraphed faces are usually hidden, a block from presented here has produced convincing results mainly on the reign of Hatshepsut (middle of 15 th century BC) is magmatic rocks, which are granular and heterogeneous such as accessible through a small gap (Figure 5). Unfortunately, it is the granitic stones from Aswan. too narrow to get a complete photography cover of the hidden As presented by (Capriotti Vitozzi & Angelini, 2013), the inscriptions, and even more for the epigraphist to produce a recent evolutions in image reconstruction can be tweaked to facsimile from a plastic sheet. provide additional information from photographs. The idea is This re-employed block studied by S. Biston-Moulin (to be to take advantage of the depth information through a published) is a subject of interest, as only few traces remain photogrammetric process to get another view of the carvings from the queen's reign. About 15 cm at the most narrow spots, made on an object. Generally deeper than the breaks, a proper the gap is still wide enough to slide a camera and take images. acquisition and 3d reconstruction make these appear more Too small for a DSLR, a Coolpix compact camera was used. clearly than with a trained eye on the field, as the stone texture A mirror was reflecting the light from the sun towards the -here invisible- does not mislead the reading. Three examples engraved face, providing a diffuse lighting on the whole can illustrate the results achievable through the technique. surface. The camera was then moved horizontally and vertically from a few centimeters for each poses, literally This contribution has been peer-reviewed. doi:10.5194/isprs-archives-XLII-5-W1-357-2017 361  The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Volume XLII-5/W1, 2017 GEOMATICS & RESTORATION – Conservation of Cultural Heritage in the Digital Era, 22–24 May 2017, Florence, Italy Figure 7: Depth maps application on temple furniture: the case of the support of Sekhemre-Seouadjtaouy (XIIIth dynasty) in the “Middle Kingdom court”. Figure 8: Depth maps application on hammered royal stele in granodiorite from the First Court. The first application case is a granite piece of furniture from monument's ceiling. The depth maps revealed some very thin the 13th dynasty (first half of the 18 th century BC), on which a and flattened inscriptions, as well as continuous drawings dedication banner spreads around the four faces (Labarta, elements (Figure 9). 2017). The banner is in a very bad conservation state, as the stone has been eroding year after year along subparallel faces. 3.2.3 On the use of historical images: The "Cour de la The carvings are not deep enough, or too much degraded on 2 Cachette" holds its name from the discovery by G. Legrain of faces, but inscriptions clearly pop out from the depth maps more than 800 statues and 17000 bronze statuettes between computed on the two other sides (Figure 7). The method proves 1903 and 1907. The profusion of elements to unearth combined to be effective as some of the signs had not been mentioned in to the conditions of the excavation (up to 15 meters deep, the first (and unique) hieroglyphic transcription of the furniture in 1950's. The second example relies on the study of a royal stele made of granodiorite. Its inscriptions have been voluntarily hammered (Figure 8), as it happened for various reasons along the history of Egypt. G. Legrain, a prominent Egyptologist that led Karnak reconstruction in the early 20 th century, found the stele and wrote about it : “The name carved in the cartouches seem to be Nekhao (?). A historical twenty lines text was carved above the scene, but its deplorable state of conservation prevents from reading it. It seems to be dating from the year 6” (Legrain, 1929) 2. Currently under study, the date of the year 6 has been confirmed on the first depth maps but it also appears that the proposed main dating must be analyzed again. It is hoped that the technique will help to confirm the king mentioned as well as the nature of the text that could be linked to a drawing of a sacred bull in the offering scene from the stele’s upper part. The third and final example illustrates how the technique can be used for architectural reconstruction purposes. During the study of the epigraphic inscriptions on the central bark shrine Figure 9: Depth maps application on architectural blocks: the of Philip Arrhidaeus (323-317 BC) (Thiers & Tillier, case of ceiling fragments from the Central Bark Shrine in forthcoming), two blocks have been identified as part of the granite. This contribution has been peer-reviewed. doi:10.5194/isprs-archives-XLII-5-W1-357-2017 362  The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Volume XLII-5/W1, 2017 GEOMATICS & RESTORATION – Conservation of Cultural Heritage in the Digital Era, 22–24 May 2017, Florence, Italy groundwater penetration,...) have been obstacles for a proper The amount of data accumulated will likely, at some points, and complete documentation of the findings. No precise survey become so massive that it will require too much workforce to was made, leaving the archaeologists with a doubt about the be analysed, exactly as the 2 km² area is complicated to fully limits in which the diggings happened. study on the field. The developments in the image recognition The photographic archive is made of about 50 images of the and classification fields could help to automatically extract scene, taken by G. Legrain as well as professional and amateur semantic elements, as presented by (Franken & van Gemert, photographers. They have been lying in boxes for decades, 2013, Nederhof, 2015). Projet Karnak’s database, designed to serving as a graphical documentation along with sketches and index every inscriptions on the walls of the temple, is expected historical texts. to continue its growth upward the current 8500 documents. (Egels & Laroze, 2015) present how modern algorithms can Associating images, hieroglyphs, transliteration and help to solve an old problem. Taken at different times with translation, it constitutes a reliable learning base that could be various cameras, the orientation of the images is the first issue helpful for neural machine approaches. to solve. The SIFT and ANN algorithms can detect and match a It might be risky to bet on the future, but one surely can be sufficient amount of tie-points, however the external confident that the forthcoming material and technical orientations are tricky to determine using today's classical improvements will be a great help to build a global and camera models. The focus differences as well as focal length thorough preservation of our most magnificent cultural changes have been neglected (experiments with individual heritage. These advances are however hardly imaginable calculations led to small differences), but a high decentering without collaborations with various research centers, as they variable has to be applied to take into account the specific have shown through time how impacting they have been. cameras which were adapted to the lack of tripod heads. A 3D model has been calculated using dense correlation algorithm. It 5. CONLUSION is a helpful document to clarify the limits of the excavation, as well the position of some of the statues before they got The article presented the historical evolution of the use of unearthed. image processing, starting 50 years ago. After a few Still under study, the lack of pictures is the main obstacle for a experiments, the technique proved to be effective but costly, full documentation of the process. Some images can not be reserved to a few experimented people and specialized oriented properly as not enough tie-points could be found (even equipment, out of the range of an archaeological mission. The manually) to orientate the whole archive, or it is simply not recent automation advances, made possible thanks to the possible to derive reliable 3D information due to the lack of collaborations with the computer vision community, have overlap. It is hoped that more pictures will be found in the drastically mitigated these drawbacks. As of today, the future to correct that problem. techniques described in the article have deeply impacted the nature of the field work. It benefits to the research center as a 4. FUTURE tool for the study of the temple, of the objects and furnitures, as a communication tool, and it stimulates the innovative spirit Computer vision and photogrammetric processes are already of the team which finds original applications while not being adopted by many within the research team. It is wished to experts in that specific field. The future is by nature hard to integrate these systematically in the process of the study of the predict but it is expected that the technological revolution we collapsed structures, among which two projects started to study are living will continue to benefit to the study and conservation the epigraphy of the 7th pylon and the Taharqa edifice. Iconem’s of the cultural heritage. Collaborations with interested research ambition is to preserve the knowledge of threatened heritage institutes, universities or companies have proven their value in using digital advances. Aiming at producing real digital the past, as they still impact the present work. They are still doubles of archaeological remains or expanses, Iconem will warmly welcome, especially to overcome the challenge of a bring its expertise in these projects, offering the scientific digital copy of the entire temple including all the hieroglyphic community and the public an innovative means of exploring inscriptions and details as thin as graffitis. famous places of world heritage. The rise of 3D modeling is not only due to the advances in ACKNOWLEDGEMENTS image reconstruction. It benefited from both the laser scanning and the Unnamned Aerial Vehicle (UAV) techniques, which This project is supported by LabEx ARCHIMEDE from both improved substantially in the recent years. Laser scanner "Investissement d’Avenir" program ANR-11-LABX-0032-01. are getting quicker and cheaper year after year. Some of these The authors would like to thank the Ministry of Egyptian tools are in the same price range as good cameras, and rather Antiquities, Abd Al Sattar Badri and Christophe Thiers, co- than a competitor, they can be used in combination with these, directors of the CFEETK and Amin Ammar, General Director especially terrestrial laser scan and UAV photogrammetry of the temples of Karnak for their daily support and help. (Eisenbeiss & Zhang, 2006). Special thanks to Mrs Chiara Salvador (doctoral researcher at The developments of UAVs is also popular thanks to the quick the University of Oxford) and to Mr Hervé Lançon (CEO of drop in the sensors price (IMU, GPS,…). More and more Sites SAS). reliable, various sensors can be carried out, providing additional information. The famous (Scan Pyramids Mission, REFERENCES 2016), and its impact both as a scientific, a historic and a communication tool, is a clear argument for that cause, Azim, M., Bjarnason, Fr., Deleuze, P., 1998. Karnak et sa although they are still complicated to use due to the regulation. topographie, Vol. I, CRA, 19, Paris. They could be a major asset to get the best viewpoints of remote objects, as the top of the obelisks that can reach up to Biston-Moulin, S., Thiers, Chr., 2016. Le temple de Ptah à 30 meters high. It is hoped to be able some day to cover the Karnak I. Relevé épigraphique (Ptah, nos 1-191), II. Relevé whole area with such a tool. Integrating a global 3D model in photographique (J.-Fr. Gout), Travaux du Centre Franco- which the documents in the Projet Karnak would georeference Égyptien d’Étude des Temples de Karnak, BiGen, 49, Le Caire. each of the historical findings would be a major advance in the digital conservation of Karnak. Brand, P.F., Laroze, E., Revez, J., 2013. Le projet américano- canadien de relevé des colonnes de la Grande Salle Hypostyle This contribution has been peer-reviewed. doi:10.5194/isprs-archives-XLII-5-W1-357-2017 363  The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Volume XLII-5/W1, 2017 GEOMATICS & RESTORATION – Conservation of Cultural Heritage in the Digital Era, 22–24 May 2017, Florence, Italy de Karnak : objectifs globaux et méthodologie, JSSEA, 38, Proceedings of the XXth Congress of the ISPRS, Istanbul, pp. 17-34. Turkey, pp. 12-23. Capriotti Vittozzi, G., Angelini, A., 2013. Una ricerca tra Meyer E., 2005. La photogrammétrie pour le relevé antichi disastri ambientali tecnologie avanzate in R. Pirelli épigraphique des colonnes de la Salle Hypostyle du temple de (éd.), Ricerche Italiane e Scavi in Egitto, 6, Cairo, pp. 81-96. Karnak, Revue XYZ, 102, pp. 29-34. Charloux, G., Thiers, Chr., 2017. The early temple of Ptah at Nederhof, M. J., 2015. ORC of handwritten transcriptions of Karnak. Egyptian Archaeology, (50), pp. 11-15. Ancient Egyptian hieroglyphic text. Altertumswissenschaften in a Digital Age: Egyptology, Papyrology and beyond, Leipzig. Charloux, G., Thiers, Chr., Abd al-Aziz, M., Ali al-Abady, M ;, Bout, St., Bourse, C., Laroye, J., Guadagnini, K., Nasseh, A. Remondino, F., Fraser, C., 2006. Digital camera calibration The Afterlife of Egyptian Statues: New Evidence From a Cache methods: considerations and comparisons. International of Cultic Objects in the Temple of Ptah at Karnak, Antiquity Archives of Photogrammetry, Remote Sensing and Spatial (forthcoming). Information Sciences, 36(5), pp. 266-272. Chandelier, L., Chazaly, B., Egels, Y., Laroze, E., 2009. Rosenberg, P., 1955. Information theory and electronic Numérisation 3D et déroulé photographique des 134 colonnes photogrammetry. Photogrammetric engineering, 21(4), pp. de la Grande Salle Hypostyle de Karnak, Revue XYZ, 120, 543-555. pp. 33-39. Scan Pyramids Mission, 2016. Press release, Cairo, Egypt. Chandelier, L., 2011. La prise de vue photogrammétrique. http://www.hip.institute/press/HIP_INSTITUTE_CP9_EN.pdf. http://cours-fad-public.ensg.eu/mod/resource/view.php? Last access : Apr. 1th 2017. id=495&redirect=1 Thiers, Chr., Tillier, A., Le reposoir de barque de Philippe Chazaly, B., Laroze, E., 2005. Le relevé par scannage 3D du Arrhidée. Relevé épigraphique, Le Caire (forthcoming). temple d’Opet à Karnak, Egypte, Revue XYZ, 102, pp. 21-26. Vergnieux, R., Gondran, M., 1997. Aménophis IV et les pierres CloudCompare (version 2.9) [GPL software], 2017. Retrieved du soleil. Akhénaton retrouvé. Arthaud, Paris. from http://www.cloudcompare.org/ Vergnieux, R., 1999. Recherches sur les monuments thébains Egels, Y., Laroze E., 2016, November. From photographic d’Amenhotep IV à l’aide d’outils informatiques. Méthodes et archives to 3D data: experience of the “Cour de la Cachette” at résultats, CSEG, 4, Genève. Karnak, CIPA Newsletter 10, pp. 1-2 http://cipa.icomos.org/portfolio-item/newsletter_10/. Yoyotte, J., 1966. Religion de l'Égypte. École Pratique des Hautes Études: Ve section - sciences religieuses, 79 (75), Eisenbeiss, H., Zhang, L., 2006. Comparison of DSMs pp. 267-282. generated from mini UAV imagery and terrestrial laser scanner in a cultural heritage application. International Archives of APPENDIX Photogrammetry, Remote Sensing and Spatial Information 1 Sciences, 36(5), pp. 90-96. Based on a comprehensive inventory of documents and inscriptions from Karnak collated in the field, this project is Franken, M., van Gemert, J. C., 2013. Automatic Egyptian available in http://sith.huma-num.fr/karnak hieroglyph recognition by retrieving images as texts. In Proceedings of the 21st ACM international conference on 2 Original french text from G. Legrain on the study of the royal Multimedia, pp. 765-768. stele : “Le nom gravé dans les cartouches paraît être celui de Nekhao (?). Un texte historique d’une vingtaine de lignes était Frood, E., Howley, K., 2014. Application of Reflectance gravé au-dessous du tableau, mais son état déplorable en Transformation Imaging (RTI) in the Study of Temple Graffiti. empêche le déchiffrement. La date paraît être l’an VI.” In Pischikiva, E., Budka, J., Griffin, K. (ed.), Thebes in the First Millenium B.C., Cambridge, pp. 625-638. 3 The Macedonian king Philip Arrhidaeus dedicates (repeatedly Labarta, Ch., 2017. Un support au nom de Sobekhotep in the wall inscriptions) his construction to Thutmose III, king Sékhemrê-Séouadjtaouy – Karnak varia, Karnak, 16 of the 18th dynasty and builder of the previous shrine which (forthcoming). was erected in the same place and performed the same function (Biston-Moulin & Thiers, 2017). Furthermore, this assignment Laroze, E., Chazaly, B., 2009. Relevés des colonnes de la proposal is based on a typological study of starry decoration, grande salle hypostyle de Karnak, CRAIBL, 153(2), pp. 669- also carried out using depth maps. 686. Legrain, G., 1929. Les temples de Karnak. Fragment du dernier ouvrage de Georges Legrain, Directeur des Travaux du Service des Antiquités de l’Égypte, Bruxelles, p. 140. Le Saout, F., 1982. Reconstitution des murs de la Cour de la Cachette. Karnak, 7, pp. 213-58. Meyer, E., Grussenmeyer, P., Tidafi, T., Parisel, C. and Revez, J., 2004. Photogrammetry for the epigraphic survey in the great hypostyle hall of Karnak temple: a new approach. In This contribution has been peer-reviewed. doi:10.5194/isprs-archives-XLII-5-W1-357-2017 364