Web Exclusive: Scanning History
July 1, 2010
When future generations want to learn about Mission Concepción, Mission San José, Mission San Juan, Mission Espada and the Espada Aqueduct, the oldest continually used aqueduct in North America, they’ll have new tools at their disposal thanks to a state-of-the-art digital scanning project recently completed by Critigen and CyArk in San Antonio. “The scans produced essential documentation for ongoing restoration efforts and created valuable resources for K-through-12 education and cultural tourism,” says John Brown, Critigen’s senior 3DLS practice leader.
Critigen used a laser scanner to record millions of highly accurate, unique points by sweeping its beam over the missions and aqueduct. The scanners’ X,Y,Z measurements are recorded and displayed as a point cloud that can be viewed, measured and navigated as a 3D model, providing incredible insight to the scene. The San Antonio Missions digital preservation project provided a 3D digital model capable of recreating built surfaces with an accuracy of less than 1 centimeter.
The Scanning AdvantageTypically, to determine “as found” conditions in environments such as the San Antonio Missions, designers will go into the field with drawings, take copious measurements and photographs, return to their desks and design the system. Often the designer realizes that they have missed a piece of information, or a component has changed, and they must return to the field and re-measure.
This manual process takes time and can be prone to error. In fact, field rework often runs between 3 to 5 percent of a surveying contract. The use of 3D laser scanning (which Critigen refers to as 3DLS) as a tool to define the “as-found” conditions mitigates these errors and reduces the potential strain of physical measurement on historically important-and potentially fragile-environments such as the Missions. In a matter of minutes, complete surface geometry of a structure is safely and accurately captured.
The 3D model provides realistic digital information of the San Antonio sites and has applications to provide innovative and interactive public interpretation, education, research and security programs. With the digital models, the National Park Service (NPS) plans to develop a realistic interactive tool for the San Antonio Missions for potential virtual tours of the sites. The 3D models of the Missions and associated structures can also be used to create digital educational games for K-12 students.
The models also provide an extremely accurate record of the site in the event of an incident resulting in damage to the structures. The model contains the necessary data to accurately reconstruct the missions.
Applied 3DLSCritigen often uses 3D laser scanning technology in critical infrastructure projects-defined as the assets that are essential for the functioning of a society and economy–including water, transportation, waste and energy, among others. But it’s the same benefits that aid in modernizing facilities, pipe galleries, bridges, overpasses, and disaster areas that are now making San Antonio’s history accessible to a new generation. Laser scanning creates unmatched visualization data with high density, accurate data, speed of data capture, safety and convenience of remote acquisition and measurement, 3D visualization and digital imagery. “3DLS is particularly effective for measuring existing features in high-density, inaccessible, or hazardous environments,” Brown says. “The end result is a detailed, geometrically accurate, photorealistic documentation of any physical environment.”
The abundance of data captured in laser scanning reduces questionable data and provides over-sampling to optimize accuracy and ensure all objects, structures and geometry are recorded. The capture of high-point-density data ensures a complete topographic survey: All details are captured, and all data captured are direct measurements.
“Geospatial technology such as 3DLS is being combined with location-based data and business information to create a powerful solution for public and corporate problems,” Brown says. “The Missions work is a fine example of the technology, but it’s just the tip of the iceberg. It's a burgeoning business sector.”