Version classiqueVersion mobile
OpenEdition Books

Excavations at Sissi

 | 
Jan Driessen

11. The use of a virtual tour during excavation

Thibaut Gomrée et Lina Manousogiannaki-Gomrée

Texte intégral

1The virtual tour is a panoramic photo which can be developed into a film, hence allowing the viewer to discover a 360° horizontal and 180° vertical view of the theme photographed, with only a simple movement of his/her mouse. This tool is used for a variety of purposes, including the internet presentation of hotels, remarkable landscapes, inside views of museums etc. This way, future visitors are able to gain an overall impression of their chosen destination. Archaeologists have used panoramic photographs for scientific purposes in the past (van Effenterre 1980: 69, fig. 92; van Effenterre 1966: 62; Soles 1979: pl. 19, fig. 7). The aim of this type of documentation was evidently to acquire an overall view of the place examined in each case, whether it was during a survey or an excavation. However, such pictures have usually covered only a limited part of the location in question. In order to be more effective, we propose the realisation of 360° pictures which subsequently can be turned into a film. During the 2008 excavation campaign at Sissi, a number of virtual tours were made. The point of this brief presentation is to assess whether such a tool is useful to record an excavation and whether the resulting film has significant scientific utility and importance.

1. The Method

  • 1 For some virtual tours made by L. Manousogiannaki in 2006 during the excavation of Jean-Pierre Bru (...)

2Several ways to produce a virtual tour exist. These depend on the aims, the equipment and the computer programmes that the photographer decides to use and the specific topic of interest that he decides to photograph. Here we attempt to explain our approach in constructing a virtual tour, as used at Sissi. The virtual tour consists of several photos taken on a fixed axis, while the camera performs a 360° turn around itself1. The views taken are assembled in one photograph which will be turned into a film commonly known as the virtual tour.

2. Taking the pictures

3Obviously, in order to acquire the best result possible, a tripod needs to be used which is provided with a panoramic head, allowing the camera to turn with precision. Such heads offer the possibility of different degrees of turns, so the quantity of the photos will vary according to the available photographic equipment. In the case of Sissi, a fisheye lens was used. Such lenses reproduce an image of 180°, i.e. from one side to the other on a horizontal axis. By turning the camera vertically, we get a field view of 60°. Therefore, six pictures of the vertical view are necessary in order to cover 360°.

4A major issue concerning the quality of the images is light. As many of us who dig in Greece during the summer have noticed, the luminosity during the daytime varies from very to extremely strong. Therefore, taking pictures in the middle of the day is a less than wise choice. Moreover, taking pictures in trenches that are quite deep often involves problems with shadows, which can result in images that are either black with no light at all or that are ‘burned’, i.e. under direct sunshine. To avoid problems such as these, we propose the bracketing technique. Bracketing consists in photographing the same item using different exposure settings. This technique is especially useful in situations of different luminosity over a single subject, such as sunshine and shadows appearing on a landscape. Bracketing can be very helpful in covering the different lights and shadows created by the natural surroundings. We have preferred to use exposure bracketing which actually implies taking three pictures, one taken in normal settings, one overexposed and one underexposed. The difference of luminosity in these three images was determined to two stops – in photographic terms – producing the same image four times brighter and four times darker. So if the shutter speed was originally set at 1/60, the underexposed image would be shot at 1/250 and the overexposed at 1/15. The integration of these three assembled images produces a single unique photo of a high dynamic range, which covers all phases of luminosity that the human eye can see. As we explained earlier, in order to cover the 360° view, six images are needed. However, if we decide to use bracketing we are automatically going to take three pictures for each of these six images. So the original number of photos taken would be eighteen.

5Another point worth mentioning is the aperture chosen for the images. The aperture is the setting which controls the amount of light reaching the film. We have chosen a small aperture (from f16 to f32 depending on the capacity of the camera). Choosing a small aperture means that we can obtain more details on a picture, from foreground to background.

3. The Procedure

6The actual procedure for the virtual tour is carried out in three steps. First, we assembled the bracketed images into a single picture (fig. 11.1-4). After having done so for all of the images, we obtained six HDR (High Dynamic Range) photos for each panorama.

Fig. 11.1. ORIGINAL PHOTOS RESULTING INTO A BRACKETED IMAGE (ZONE 3, DETAIL OF EAST LIMIT)

Fig. 11.2. ORIGINAL PHOTOS RESULTING INTO A BRACKETED IMAGE (ZONE 3, DETAIL OF EAST LIMIT)

Fig. 11.3. ORIGINAL PHOTOS RESULTING INTO A BRACKETED IMAGE (ZONE 3, DETAIL OF EAST LIMIT)

Fig. 11.4. ORIGINAL PHOTOS RESULTING INTO A BRACKETED IMAGE (ZONE 3, DETAIL OF EAST LIMIT)

7The next step is the stitching of these HDR images into a single final panoramic photo with a horizontal view of 360° and a vertical view of 180° (fig. 11.5).

Fig. 11.5. ASSEMBLED IMAGES TO A PANORAMA (INSIDE BUILDING 2)

8Next, we can correct the contrast or saturation or whatever is considered necessary using Photoshop (fig. 11.6).

Fig. 11.6. IMAGE AFTER CONTRAST CORRECTION IN PHOTOSHOP

9Finally, a third step is to create a film on a Java or Quick Time movie extension of this image. Once the process is completed we can zoom in or out on the film or we can ‘walk’ around it, using our mouse cursor. This last step cannot – of course – be printed, but one can take a look on the website at http://www.sarpedon.be for a final view of the process.

10All programs used for these different processes can be found on the internet, commonly under the term of panoramic tools.

11Some examples of virtual tours of Sissi were made at the end of the second excavation campaign. Almost every sector was photographed in detail, offering the possibility of being turned into virtual tours afterwards.

4. The Interest of Virtual Tours

12A virtual tour offers many different advantages for a site under excavation. First of all, there is a clear didactic utility. Since the distortion of the image is very high, the images can evidently not be used to assist any type of drawing. However, these same images, as films, can be used to aid in oral presentations, giving a good account of the spaces excavated. In this way, the audience can actually see and not merely imagine the excavation, the surroundings of the site and even the detail of a room or a wall or, in some cases, even the floor. With the cursor of the mouse, one can approach or move back on the film in order to examine a small detail that struck the eye during excavation but was later forgotten. It is a visual tool which enables us to place ourselves back to the ‘scene of the crime’.

  • 2 At Sissi, two DVD entries commented by the area supervisors are made a day for each trench with ad (...)

13A second advantage concerns the archaeologist himself. He is able to return to the trench at a specific time of choice, provided that several tours were made at different intervals during the excavation. This allows one to actually document the general progression of the work during the campaign. Moreover, unlike filming which usually focuses on details that are important at the time when the excavation is taking place, the virtual tour gives a more generalized aspect of the space2.

14Obviously a virtual tour is not the ultimate method for recording an excavation. Aerial photography (by kite or other means) certainly gives a better idea of the overall plan and horizontality of a site. This may not always be available and the relatively low cost of the material needed for a virtual tour places it amongst the most cost-effective ways of documentation. One should also keep in mind the facility of transport and setting-up of the material and, of course, the fact that its implementation is not as depended on the weather as some methods of aerial photography, which means that one can use it at every given moment. Finally, the processing of the photos can be done rapidly and one can take a look at the results within half an hour.

15The advantages mentioned relate to the use of a virtual tour for providing more information on a classical architectural plan. What we suggest is that, if the tripod has been geo-referenced, it is also possible to achieve a view of a general plan by clicking on the desired point, while also having a view of the space in a photographic reality, which is quite close to the reality of the eye.

16To conclude, it would be interesting to advance the technique by making photos without distortion allowing their use in order to make a 3D reconstitution of spaces but also to use them as references for drawings. We are currently developing this angle.

17A virtual tour thus has an interest for an archaeological excavation and for the presentation of its results. Easy to use, quick, at low cost, it is a tool for additional documentation adding something more to all the other means that are already used.

Bibliographie

5. References

▪ Van Effenterre 1966 = H. van Effenterre, Mallia 1956-1965 : dix années de non-conformisme, Archéologia n°9 (1966), 60-65.

▪ Van Effenterre 1980 = H. van Effenterre, Le palais de Mallia et la cité minoenne, Rome, 1980.

▪ Soles 1979 = J.S. Soles, The Early Gournia Town, AJA 83 (1979), 149-167.

Notes

1 For some virtual tours made by L. Manousogiannaki in 2006 during the excavation of Jean-Pierre Brun at Pompeii see http://www.centre-jean-berard.cnrs.fr/.

2 At Sissi, two DVD entries commented by the area supervisors are made a day for each trench with additional recording of each significant feature.

Table des illustrations

Légende Fig. 11.1. ORIGINAL PHOTOS RESULTING INTO A BRACKETED IMAGE (ZONE 3, DETAIL OF EAST LIMIT)
URL http://books.openedition.org/pucl/docannexe/image/470/img-1.jpg
Fichier image/jpeg, 145k
Légende Fig. 11.2. ORIGINAL PHOTOS RESULTING INTO A BRACKETED IMAGE (ZONE 3, DETAIL OF EAST LIMIT)
URL http://books.openedition.org/pucl/docannexe/image/470/img-2.jpg
Fichier image/jpeg, 74k
Légende Fig. 11.3. ORIGINAL PHOTOS RESULTING INTO A BRACKETED IMAGE (ZONE 3, DETAIL OF EAST LIMIT)
URL http://books.openedition.org/pucl/docannexe/image/470/img-3.jpg
Fichier image/jpeg, 86k
Légende Fig. 11.4. ORIGINAL PHOTOS RESULTING INTO A BRACKETED IMAGE (ZONE 3, DETAIL OF EAST LIMIT)
URL http://books.openedition.org/pucl/docannexe/image/470/img-4.jpg
Fichier image/jpeg, 157k
Légende Fig. 11.5. ASSEMBLED IMAGES TO A PANORAMA (INSIDE BUILDING 2)
URL http://books.openedition.org/pucl/docannexe/image/470/img-5.jpg
Fichier image/jpeg, 112k
Légende Fig. 11.6. IMAGE AFTER CONTRAST CORRECTION IN PHOTOSHOP
URL http://books.openedition.org/pucl/docannexe/image/470/img-6.jpg
Fichier image/jpeg, 127k

© Presses universitaires de Louvain, 2009

Conditions d’utilisation : http://www.openedition.org/6540