Photogrammetry training in Al-Ula

Workshop in Al-Ula, Saudi Arabia - Sept-October 2018

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Factum Foundation’s Otto Lowe spent two weeks in the town of Al-Ula, in the Kingdom of Saudi Arabia, teaching a group of fifteen locals how to record cultural heritage in 3D using photogrammetry. It was a collaborative pilot project between the Factum Foundation, Art Jameel, and the Royal Commission of Al-Ula (RCU), and generously funded by Jacob Rothschild. The course took place between the 30th September and 11th October at the Shaden Resort, and involved a class of 10 women and 5 men.

Over a period of seven days, the students recorded at three different sites in the vicinity of Al-Ula. More than 74,000 images were recorded in this time period, with the entire project weighing a total of 1.29TB.

The first two days of the workshop were dedicated to teaching the theory behind photogrammetry. The core concepts behind the process of photogrammetry were explained alongside a more technical explanation as to what a 3D model is, as well as a brief overview of how to use the Reality Capture software. Fatima Mazeh from Art Jameel, who was initially supposed to be supplying translation for the technical terms, became crucial as a full translator. 

The classroom at the Shaden Resort. Image by Annette Gibbons-Warren (RCU)

On the the second day of the theory workshop, Otto performed a practical demonstration of photogrammetry outside the classroom. This live presentation of image capture and processing not only gave the students a much better idea of the steps involved and prepared them for the coming days of recording in the field, but provided further inspiration for the tough task ahead, evident through their visible excitement at the speed at which results could be seen.

Live photogrammetry demonstration. Image by Annette Gibbons-Warren (RCU)

After exploring a number of potential sites to be recorded by the students, most notably a six metre panel featuring petroglyphs of ibex and a rock carved with a petroglyph of an ostrich, it was decided upon arrival to select two more recently discovered sites, including one shown to us by a student, due to their greater suitability for a large group. These were chosen alongside the Lihyanite Library at Jabal Ikhmah, a UNESCO world heritage site. 

Site 1

On the third the group travelled to Jabal Ikhmah to begin the recording of the site, with two of the days devoted to this. The site, a valley covered in writing and inscriptions, is an ancient meeting place where the Lihyanite kings used to inscribe their laws and edicts. Despite it being closed off to the general public for its protection, the RCU were able to acquire special permissions in order for us to be allowed to work there. 

On the first day of the scanning there, a film crew was there to make a video of the workshop at the request of the RCU. This provided valuable time in the evening, after the students had left, for Otto to conduct a general recording of the entire site, while the film crew were capturing magnificent shots of the site. This general recording proved extremely useful as it allowed Otto to align the individual work of the students within a larger context. 

On the second day at Jabal Ikhmah, Otto decided to show the students how to do this form of general recording; this involves capturing a series of panoramic photographs from several different positions. Whilst this allows the rapid recording of an entire site, more minute detail is sacrificed as a result.

The students were lined up on one side of the valley with approximately four metres between them, with each student doing three panoramic positions. Once this was done, they switched to the other side of the valley and did the same again. 

The alignment of one half of the student’s general scan

After the lunch break, the students came back to the site and continued doing close range photogrammetry of the rock carvings. Some of the men had long range lenses and these were put to use recording the carvings that were too high up and otherwise inaccessible. The women, due to their abayas, were limited to working from the ground, while the men, who were in more flexible clothing, were able to scramble up to the harder to reach areas. 

During this afternoon session Otto and one of the women were able to focus in-depth on the ‘Hero Stone’, which was highlighted by Annette as the most important piece at the site. 

Following the recording at Jabal Ikhmah, a day was devoted to showing the students the fruits of their labours. The morning was spent showing the students examples of what they had done and going through the strengths and weaknesses of how they had taken the images. 

This allowed the students to identify some of the mistakes being made, such as not capturing enough images as well as not getting close enough to the object they were recording (both common difficulties for anyone first learning photogrammetry), in order to learn and improve over the coming days. By the end of the course, these issues had been completely resolved. 

During the afternoon session, the students were instructed on how to use Reality Capture. Some of the women had already downloaded the programme and had done some basic alignments. The students were taught how to navigate essential features of the software, like scaling and reconstructing a mesh. Some of the students personally downloaded either Reality Capture or Agisoft Photoscan and Otto was able to provide some further instruction on how to use each programme to those individuals. 

Overall, the students did incredibly well in their first experience of recording. They were able to record a good level of detail which was demonstrated during the Thursday class. 

 

 

Site 2

When the course restarted on Sunday, the students were taken to the second site which was a cliff face, roughly fifteen metres wide, which was covered in petroglyphs. This had been supplied by archaeologists who were working in the area, who had provided GPS coordinates with the sites location. Luckily, the site was located in close proximity to the road and thus was easier to access by bus than any of the other sites recorded. 

The morning session was dedicated to the general recording of the site. Once again, the students were lined up in front of the cliff and were asked to do panoramic photography from set positions. 

The students lined up doing panoramic photography. Photo taken by Otto Lowe

 

The students were then put to recording the petroglyphs in detail. Once again the men were set to recording the difficult areas and the more out of reach drawings; the women recorded the petroglyphs at ground level.

 

 

Site 3

Over the weekend, the student had shown us a long gully covered in epigraphy from a variety of different time periods, which subsequently became our third site. 

This was the largest of the three sites meaning three days were devoted to its recording. The gully was effectively split into two parts, with the second half involving climbing down a drop; because of this the recording was split into two halves. The first half was recorded on the first day, the second half on the second day, with the third day devoted to recording both halves in such a way that the datasets would merge seamlessly together. 

As with the previous two sites, the students were asked to conduct a general recording using panoramic photograph from set positions. They then proceeded to get closer and do precise recording of individual sections. Owing to the large amount of epigraphy, and its relatively shallow depth, the students’ scanning sessions were organised in such a way that every section was effectively recorded twice, to ensure that the detail would be captured thoroughly.

 

 

 

The processing of the third site has proved to be the most challenging of the three given its larger scale and that three whole days were dedicated to its recording. As a result, this vast amount of data, consisting of thousands of photographs taken between fifteen students, is still being processed back in Madrid.

Overall, the training at Al-Ula highlights the significance of photogrammetry as a way of providing local people with the technology and accompanying skill-set required to take the preservation of cultural heritage into their own hands. This educative initiative is one of the most significant in Factum Foundation’s recent efforts to support the dissemination of digital recording skills and technologies across Saudi Arabia.

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