As for the pros of laser scanning as a documentation process for historic buildings, there are plenty. Laser scanners can gather millions of bits of information in a single scan. Scanners can gather information from dangerous/hazardous locations, difficult to reach areas or extreme heights. Scanners provide access to data that would otherwise be very costly and/or even dangerous to obtain. Scanners also provide a level of detail that cannot be found with even the most high resolution cameras.
|Photo Courtesy of History San Jose|
Documenting pottery, turn of the century kitchen utensils, furniture and tools are all appropriate applications and areas where this technology shows tremendous promise. At times, the upside of this technology and its applications appear endless.
|Freedom Papers Of Sampson Greaves filed with Santa Clara County Recorders in 1854|
Photo Courtesy of History San Jose
Though the arguments in favor of this technology are loud and clear, some of the challenges to the expanded applications are glaringly apparent. First and foremost, reality capture technology is much like basic photography; "it's line of sight" technology. The laser can only see what is in its direct path. Anything that is blocked, obscured or invisible to the laser's beam cannot be documented. Therefore to avoid physical barriers to the scanning process like bushes, fences and other obstacles, multiple scans from various angles must be performed to get the full benefit of the technology. The time required to set up and complete a scan, relocate the scanner for the next set of scans can be a bit much, especially when working under strict time constraints. Thus, when dealing with small, multi-room structures it may be easier, less time consuming and less costly to utilize hand measurement tools. (Conversely, the documentation of large, open facilities such as auditoriums, convention halls or warehouses are an ideal applications for this technology.) These visual limitations obviously extend to other areas such as the rooftops and underneath buildings. A basic rule of thumb when using laser scanning tools is if you can't see it, neither will the laser.
Because lasers work off of an object's reflectivity, they have a very difficult time collecting data from dark colored items. This can be compensated for when incorporating texture mapping
techniques to the final product however this idea is not without its flaws. Mainly, the quality and resolution of a laser scan is extremely difficult if not impossible to match with today's photo technology. The moment the photo overlay is applied to the laser scan there is a marked reduction in quality, sharpness and to a much lesser extent, accuracy of a laser scan.
When operating the laser at lower intensity levels, the edge of the point cloud can look "fuzzy" and lack the detail necessary to take accurate measurements. Though, I'm sure the type of laser and its application has a major impact on this phenomenon. I am anxious to test the application of different models and types of lasers in a variety of situations and duties during the upcoming months of this project.
For forensic documentation purposes, the laser is unable to gather details about construction materials so certain aspects of the process require significant operator input. No matter how advance the technology, the human factor is critical to the accuracy and effectiveness of the product. This underscores the importance of this project's educational component. Through every step of the project, from the documentation/reality capture of the campus to the reality capture of and documentation of the farming equipment; the capture of all data, how it is accessed, shared and utilized will be developed through practical application in the real world environment.
Serious consideration must also be given to the long term maintenance and sustainability of electronic files and records. What happens to files that are constantly in use, altered, shared and manipulated? The deterioration of electronic files is a very serious concern that must be addressed. Redundancy, back-up systems and alternative records are essential to the documentation and preservation process. The 3D model can be used to create printable 2D floor plans, campus maps and schematics as backup and supplemental documentation.
The bottom line is a project of this magnitude will require multiple strategies to achieve the optimum results for the museum, its artifacts and the general public. Particular elements of the project will require deep forensic documentation while others may require a much less detailed accounting for condition monitoring and exhibition. In some elements, laser scanning technology may be supplemented with other documentation processes to achieve the best possible outcome for the museum's artifacts and for exhibition purposes.
As with all emerging technologies there are still questions to be answered, techniques to be mastered and applications to be discovered. Stay tuned.....