3D-scanning in the jungle

Cave entrance seen from first chamber

At the end of May I went to Belize to work at a Maya site out in the jungle for three weeks. The site, originally referred as “Awe Caves”, is a medium-sized Maya ceremonial center located in the western part of Belize. It is of particular interest because a large cave with an extensive dark zone tunnel system resides directly beneath the largest temple in the site core. The project of 3D documentation and reconstruction of this site is part of a larger research project of preliminary investigation started in the summer 2011 and directed by Holley Moyes, UC Merced. The first year some 3D documentation of the excavations was done by Fabrizio Galeazzi, UC Merced. This year one of the ambitions was to 3D-scan the complete cave. The cave is a natural geological structure, but has been divided into nine chambers in succession, by the Mayan people. The cave turns around so that the last chamber enters into the first, about 10-15 meters up on one of the walls in the entrance chamber. The different division of the chambers varies from clearly manmade structures to more or less natural boundaries.

Snapshot from pointscloud. The colored area shows a manmade wall

The 3d scanning was done with a Faro Focus 3D scanner. It is a small and compact scanner, that is easy to carry and has everything needed to scan built in. Faro Focus 3D including tripod, weighs about 8 kg and is therefore the ideal scanner for a mission of this kind. One important benefit from the small format of the scanner is evident in the fact that the scanning of the complete cave were made in just eight days.

Scanning of excavtion in the cave was done with light

Right from the beginning it was decided not to try to capture color information in the cave, but only settle for the geometry. To capture color information would demand large amounts of lights to illuminate the cave properly. Bringing enough lights and spending time placing them as good as possible would have been a huge and costly task far beyond the scope of the project.

At the start of the campaign, a fairly normal scanning strategy for larger structures was applied. This was a relatively efficient approach in the entrance chamber, but further into the cave it got more and more difficult. With such an extremely irregular geometric structure found in the cave, the risk to miss important parts was much larger than usual. So after a few days the scanning strategy significantly changed and scanning positions were moved closer together to be sure to cover as much as possible. It culminated in the fifth chamber, which was a complete jumble of rocks, stalactites, stalagmites, narrow cavities and hidden structures. This complex geometry led to a scanning strategy, in which the different scan positions were placed only a few meters from each other. This of course gave us a huge amount of scans that, at this writing, still isn’t fully post processed. 

The humidity caused other problems as well

Another objective of the scanning campaign was to verify how well the scanner handled the very special climate prevailing in a place like this. This is subtropical jungle and the work were made during a time of year when it was quite a lot of rain, high humidity and relatively warm. Inside the cave the temperature was slightly lower, but the humidity was significant. Anyone who has worked with electrical equipment in these conditions can tell you that humidity plays tricks with equipment that does not occur in dryer environments. 

Scanning part of the entrance from a spot in the jungle

We were pleased to see that the scanner handled these conditions well for most of the time. The battery ran out faster than usual, but that was expected. The only problem experienced was that the touch panel of the scanner stopped working on a number of occasions. The touch panel is mainly used to adjust the settings for the different scans, such as resolution or whether the scan should be done with color or not. Once these settings are made, the need to use the touch panel is not that big, with the very important exception of starting each new scan. Hence a non-functioning touch screen could be a serious problem. Fortunately, the scanner also provides a more stable button under the touch screen, which can be used just to start scans if you cannot start them otherwise. That saved a lot of time, since the only way to get the touchscreen to work again was to turn the scanner off and let it rest for a couple of hours. To prevent problems with humidity, the scanner bag was equipped with several small bags of silica gel during the entire period in Belize. It is used as a desiccant to control local humidity and may have done some good in keeping the scanner in such a good shape.

All in all it was a very interesting trip and we are really looking forward to have time to work with the data.

Scan of the entrancecave. To the left of the middle you can see two people that happened to be scanned. Good to use as a reference

/Stefan

Pompeii acquisition campaign second part

     

   Figure.1 Map of the insula, in green
Casa di Cecilio Giocondo

I just come back from an intense week of scanning in Pompeii, where together with Stefan Lindgren (LU), Carolina Larsson (LU), Matteo Dellepiane (CNR) and Marco Callieri (CNR) we finished the 3D acquisition of the insula V1.
Last year we focused on the houses of "Cecilio Giocondo" and "Torello di bronzo" (both part of the insula) and at the end of the campaign, we  found the time and the energies to acquired a large portion of the street that surround the insula. This year, even if the weather slowed down our work, we completed the acquisition of all the environments left from the previous campaign, closing in only two days the documentation of the insula (fig.1).

Figure 2 one of the rooms of Casa degli epigrammi greci,    

The knowledge gained last year allowed to  speed up consistently the acquisition campaign; in two days, with two teams, we collected and almost  aligned approximately 200 scans. Pompeii is really an incredible site, every small room has so many different typologies of information, even if the environments are almost empty the walls are characterized by a large  amount of details to document (fig.2).

During this season we mainly focused on the north-west and south-west part of the insula, acquiring environments such as: Casa deli epigrammi greci, the bakery,  Caupona, etc.

These areas are characterized by small and very tall rooms, all connected each others by narrow corridors and small entrances, moreover a number of containers for storage or ovens were still in their original position -bakery or the shops- and the use of the scanner for the acquisition of these rooms was not sufficient (fig.3).  In specific the containers for the storage were so close each other to do not allow any (safe) scan position. In this specific case we decide instead to acquire these elements using image based modeling techniques. This approach proved to be very successful and easy to integrate with the laser scanner data. 

Figure 3 Alignment process of the Casa degli epigrammi greci

The use of just one instrument or one technique would have never been enough to gain our goal  (fig.4). From my experience out in the field, I learned that does not exist any technique, technology or documentation platform able to cover entirelly the documentation of an archaeological site. Integration of technologies is the only proper way to face archaeological sites. Flexibility of methods is the only characteristic that allow archaeologist to develop a creative and dynamic research using technology.
I found this campaign very challenging, the environments were not easy to document, and the constant passage of tourists did not help...

Last year we worked hard to find a good workflow to post process the data and I think that this year, with some help from our students from Digital Archaeology Course we should be ready with a complete model. 

Figure 4: The Faro Focus 3D scanner inside

the oven before the scanning, 

in the picture: me, Matteo Dellepiane, and Mr. P

At the end of the project, we are also planning to connect high resolute 3D models of every room with the documentation available on the website of the Swedish Pompeii Project, in order to make accessible this work for everybody.

At the end of the campaign we decided to scan our team and leave a virtual footprint of us in the insula ;-)

/n

Insula V,1 entrance of Casa del torello di bronzo

Scanning Team in 3D, from left: Matteo Dellepiane, Marco Callieri, Carolina Larsson, Stefan Lindgren,
Nicolo' Dell'Unto