This poster was presented at the 3D Digital Documentation Summit held July 10-12, 2012 at the Presidio, San Fransisco, CA.
Post-Processing Workflows: Identifying Hidden Costs in Converting Scan Data to Useable Information
This poster aims to demonstrate the unique challenges associated with scanning and documenting OV-103 (Space Shuttle Discovery). In demonstrating the workflow and process used to get from laser scan to archival drawing, one should be able to determine the value of the product at any given stage of the process as well as assess the costs required to achieve those results. In many scanning situations it is difficult to achieve total coverage. This can be remedied in some cases,but there are times when factors are out of your control. In the case of the Shuttle, several major parts of the vehicle had been removed for servicing and cleaning. These components would not be replaced in time for scanning. In these situations, it may be necessary to supplement the missing scan data with pre-existing documentation to fill the gaps. It may also be important to note on the final documentation the various ways in which data was collected in the field and in the office. With these things in mind, the primary goal and challenge was to generate a cohesive set of interpretive and measurable drawings in a short period of time with limited access to the resource. Laser scanning addressed most of our time, accessibility, and precision concerns. In order to produce a cohesive drawing set in a limited time, several 3d modeling methods were chosen for the flexibility they could offer. Not only is a 3d model relatively easy to import and export between programs, but it offers a single entity which all drawings can refer to and draw from, producing a cohesive drawing language which help to better illustrate the site or structure from any point of view. Combining 3d models which were generated from scan data with 3d models which were generated based off of measurements obtained from pre-existing documentation forced us to utilize a variety of software. Selecting the right group of software to achieve the task was difficult indeed. Balancing newer software which offered cutting edge advantages (often beta versions) with well established industry standard CAD programs allowed us to push the envelope of a typical project without risking the integrity of the core documentation. The decision was made to let various programs do what they each do best, be it solid modeling, mesh modeling, file conversion/exporting,or line drawing. Perhaps in the future a program will exist which possesses all of these qualities, however due to the relatively younage of the industry this is not currently the case. As you may expect, dividing the tasks among various software presents some issues. Getting newer programs to speak to older ones in a common language can be difficult when proprietary file formats are involved. Training may also be required in order to properly use the unique toolsets offered in different software. Although 3d models are nice to look at on a computer screen, they must be converted into flat entities if you plan on generating them in an archivally stable manner. In this process the 3d model is primarily a tool which aides in the production of 2d line drawings or renderings. The 3d model can be used for a variety of other purposes but this assumes that the desire and ability exist to properly store and maintain the digital files in formats which are supported and maintained.
John Wachtel is a staff Architect with the Heritage Documentation Programs (HDP), producing documentation which contributes to the nation’s largest archive of historic architectural, engineering, and landscape documentation. Within the programs he focuses primarily on producing measured and interpretive drawings for engineering sites with the Historic American Engineering Record (HAER). After graduating in 2009, John accepted an internship with HAER, where he was introduced to laser scanning for the first time. For the past three years, John has been developing methods and workflows for converting laser scan data into 3D solid and mesh models to aid in the production of these drawings. He earned his Bachelor’s degree in Architecture from Iowa State University.