July 21, 2011
It’s been said that past is prologue. What happens in the past is destined to be repeated someday, like a trailer to a film that’s being remade over and over again. But do we glean anything from the past when the infrastructure and ideas that surround it have deteriorated or have been destroyed? Ancient cultures could not take photographs. Early settlers left no blueprints. We need to somehow reconstruct the past by documenting the existing infrastructure and symbols that have been left behind and then reestablishing what has been lost.
Increasingly, laser scanning technology is being used by researchers to record ruined ancient structures to help restore and preserve them. Archaeologists Travis Doering and Lori Collins from the University of South Florida’s (USF) Alliance for Integrated Spatial Technologies (AIST) are among those at the forefront of this movement.
The biggest part of the team’s mission is to help preserve the remnants of ancient cultures and find meaning in their artifacts. Through the effectiveness and creativity of their work, Collins and Doering also seek to enlighten and educate others about the benefits of laser scanning and other progressive spatial recording technologies versus traditional methods of site documentation.
Late last year, the AIST team worked with state and national officials to help record and preserve crumbling, historic sugar mill ruins in Florida that were constructed during the 18th and 19th centuries. The structures are made of coquina and lime rock mortars and bear the burden of 200 to 300 years of weathering and neglect. The objectives of this multiyear research project include the survey, documentation, archival investigation and analysis of the early history of Florida’s sugar industry, from its inception in the 1760s through the development of the late 1800s. The group hopes to preserve the cultural and architectural history of Florida’s sugar mills and also to maximize participation by USF graduate students in a project that encompasses historical, architectural, archaeological and anthropological facets. The results will provide national, state and local planners and managers overseeing Florida’s cultural heritage with a myriad of new data that can be used to preserve, restore and protect these valuable, irreplaceable resources.
The opportunity to demonstrate the multiple advantages of laser scanning to heritage preservation occurred shortly after the team conducted their initial work at the Dummett Sugar Mill Ruins located in Ormond Beach, near Daytona Beach, Fla. A few months after they had initially scanned the extant structures at the mill site, a portion of the mill’s north wall collapsed. Park officials needed to repair and restore the wall quickly and correctly before additional damage occurred, but a complete structural analysis would be required before comprehensive restoration efforts could commence. Collins and Doering were brought back to the site to rescan the structure in three dimensions using their FARO laser scanner.
The scanner worked quickly, spinning atop a tripod and projecting laser beams onto the targets at up to 976,000 measurement points per second. As the beams were reflected back to the unit, the scanner gathered millions of x, y and z coordinates. In general, bright surfaces reflected a bigger portion of the emitted light than dark surfaces. This reflectivity value was used to assign a corresponding grey value to each single point. This data, all within +/-2 millimeters of accuracy, was compiled into a point cloud that was then merged with color photographic information from the scanner to create an accurate 3D image of the structure post-collapse. The team used FARO Scene software to compare and contrast this new data with the scans taken prior to the wall’s collapse. Kubit Point Cloud was also used to render the 3D point clouds in a 2D AutoCAD environment for construction and architectural drawings.
The CAD drawings and 3D images produced from the team’s laser scanner and software are now used to analyze and examine additional areas of structural concern and to better understand the complex construction methods and building sequence of the ruin. The data will be used throughout the ongoing restoration process to reconstruct what the mill may have looked like centuries ago.
By bringing together datasets from laser scans and documentation surveys of historic sugar mill ruins in Florida, researchers at USF are learning more about the social dynamics and infrastructure development at these plantation sites. At the same time, they are learning improved ways of documenting and analyzing these complex ruin sites to better protect and restore features of state and national significance. Using a suite of spatial tools including the FARO laser scanner and post-processing software applications, AIST at USF is working with state and federal land managers on new ways of protecting and preserving the past. This important work encompasses centuries of state history. But for Collins and Doering, this is just the tip of the iceberg. They, and their laser scanning equipment, are working on much older and larger sites. And their job takes them to locations much more remote than sunny Central Florida.
In the Petén region of Guatemala, the air is thick. So thick, in fact, that it seems unlikely that anything--including the thin beams emitted from a laser scanner--could penetrate it. But the humidity and the trees help hide an important archaeological find in this isolated Central American jungle--ancient Maya ruins.
In May 2009, the USF team visited El Mirador, in the northern Petén of Guatemala, to document a 2,300-year-old Maya frieze. Working in collaboration with Dr. Richard Hansen of Idaho State University and director of the Mirador Basin Project, along with the Guatemalan Institute of Anthropology and History (IDAEH) and the Guatemalan Ministry of Culture and Sports (Cultura y Deportes), the AIST team produced high-resolution 3D reproductions of the carved stucco panels that characterize the structure. Considered the second largest archeological site in the Western Hemisphere, El Mirador represents a vast and biologically diverse environment, and it proved to be a great test for the team’s laser scanning gear.
In April, 2011 through a grant from the National Science Foundation (BCS-0911078), the team returned to Guatemala to scan and analyze important stone structures and sculptures at the 2,500-year-old settlement of Tak’alik Ab’aj, located on Guatemala’s Pacific piedmont. Doering and Collins again worked with IDAEH and Cultura y Deportes as well as with Guatemalan archaeologists Miguel Orrego Corzo and Christa Schieber de Lavarreda, directors of the Proyecto Nacional Tak’alik Ab’aj. The settlement is enormous--six square miles, to be exact--and it is the home of ancient carved monuments that were once used for civic ceremonies and rituals.
The site consists of several extensive terraces, some measuring more than 200 meters by 300 meters. Pre-Mayan symbolic iconography marks the stone monuments and structures that dot the landscape and tells stories of political rulers of their day. “The representations are a method of communication that is a sort of an early form of political propaganda--accounts of individual rulers and their accomplishments and how great they were,” Collins explains.
The site itself was likely used for ritual ceremonies by the culture’s ruling elite class. These ideological expressions and activities are in still in limited practice at the site today.
As with their project in Florida, the USF researchers were called upon to scan these ancient structures. Their mission was not just to record and document but also to train a team of Guatemalan researchers to use the scan data and help them implement their own technology program to better understand and preserve their national heritage. The team used the FARO scanner to create cross-sections of two of the more interesting terraces on the site.
Working in conjunction with Dominic Albanese, from the Maryland-based Direct Dimensions Inc., the team was able to acquire millimeter-accurate color data of the structures and carvings that surrounded the site. “The color scanning capabilities gave us much stronger data,” Collins says.
The Guatemalan team had been using plane tables to map the site’s archaeological features, a process that has taken decades to conduct. By using the scanner and transferring the images from Scene software to CAD, the team could capture much stronger and more accurate line work than with the manual methods.
Of course, this sort of documentation doesn’t mean much without geographical context. Using the laser scanner in conjunction with GPS equipment allowed the AIST team an opportunity to accurately locate and place the monuments and architecture into a real-world coordinate system. Collins and Doering and the AIST team were able to tie GPS control points to their scans. This data will then be fed into Guatemalan and USF research websites to create an interactive GIS database. Soon, website visitors will be able to view a map of the Tak’alik Ab’aj site and zoom to the 3D scans and terrain models of the site’s features. It’s an important step in not just cataloging a culture, but in enabling the Guatemalans to have a hand in its preservation.
Numerous historical and archaeological sites exist around the world, and each has a message to be deciphered. For centuries, we have worked to decode these messages through traditional means--tape measures, plane tables and photographs. Thanks to powerful solutions like the laser scanner, researchers are able to capture 3D data to take measurements and reconstruct deteriorating structures better and more quickly than ever before. Through the work of Collins, Doering and others, the lessons of history will come into clearer view.