When It Rains It Pours!

Mar 27, 2019 | World Heritage Archaeological Site of Quirigua in Guatemala

Field update – for several days we had light to no rain, coming only for short periods in the afternoon, but then we really got RAIN!!! For about 4 hours straight we had consistent downpours. Fortunately, our 3D Specialists working on the monument documentation (Jorge Gonzalez and Noelia Garcia) could continue scanning inside the tented structures. This did not work for the rest of the team working on landscape documentation (GPS, drone PhoDAR, imaging, and terrestrial laser scanning).

Palapa roof structures that are used to cover the carved monuments – we have now enclosed with tarps to minimize light impacts during structured light scanning. Ambient light can interfere with the effectiveness of the scanners and cause noise and problems with data acquisition. Our team, working with the Guatemalan resource management team, erected tarps around each area that we worked at with sensitive instruments.

Led by Oswaldo Gomez, the Director of the Quiriguá site, some of our team visited Group A, located about 5 kilometers northwest of the site. Prior to coming into the field, the USF DHHC GIS Analysts created a geodatabase, referencing the modern landscape to historic maps and site plans from more recent archaeological investigations, all the way back to the early maps and site plans from Alfred Percival Maudslay’s time. Using these maps in the background on our GPS units, we are able to walk to areas of interest, and relate locations of features previously encountered to the terrain we see today.

Plan of the ruins at Quiriguá (Maudslay, Alfred Percival. 1889. Biologia Centrali-Americana)

We were met by Carlos Obdulio Aldana Aldana, the owner of the property that contains Group A, and he graciously allowed us access. Group A sits high above the valley and provides fantastic views of the Motagua River, the banana plantations, the Village of Quiriguá and the archaeological site. Field methods in this area included panorama and gigapixel imaging and drone-based photogrammetric detection and ranging (PhoDAR). The PhoDAR mapping allows us to acquire detailed terrain 3D models as well as ortho-photography when combined with ground-based control targets.

Terrain documentation work in the surrounding environs of Quiriguá.

The heavy rains came quickly during our work in this area, and we were forced to stop and protect our gear. We walked back through heavy rain to Senor Obdukio’s farmhouse to breakdown and pack the equipment. On the way back, we stopped at a tienda to by six pounds of rice (dried grains such as rice absorb liquids, so this proved to be a readily available means of drying out our devices- including cell phones). Very useful hack that proved effective!

Phone covered in rice to absorb moisture – a hack that works!

Meanwhile, back at the Acropolis and Great Plaza, painstaking high resolution scanning with the structured light instruments continues. Much time is required for the staging (assembling tarps and scaffolding to reach and access all parts of these large monuments), and there is much difficulty in reaching and maintaining parallel scanning position across the face of the zoomorphs. Our team used not only scaffolding, but also worked with booms and pole extensions to completely document the carvings. Our highest resolution instruments (0.25 mm) were used on faint or areas of finer detail. This highest resolution scanning is time consuming, sacrificing scale/coverage speed for accuracy.

Working with a fiber carbon monopod with the structured light scanner to maintain parallel position and cover the entire surface of the complex and large zoomorph monument.

Working with the high resolution structured light instrument to capture fine details and faint or diminished glyph areas. Note that Noelia prepared for awkward positions and bending- packing kneepads that have definitely come in handy and kept her more comfortable during this hard work.