ASTM E57 – 3D Imaging Systems

A 700Kb PDF of this article as it appeared in the magazine—complete with images—is available by clicking HERE

In 2003, in response to a request from the scanner manufacturers and consumers of scan data, the National Institute of Standards and Technology (NIST) agreed to develop standards and specifications for both equipment and methods. Subsequently, the American Society for Testing and Material (ASTM) became involved. For quite some time, the playing field for scanner customers and scanning service consumers had not been level. That is, each manufacturer tended to emphasize those features that made their equipment look best. This makes it difficult for scanner buyers to effectively compare equipment, and also for consumers of scan data to evaluate the quality of the data or make informed service provider selections.

Between 2003 and 2006, NIST held four interested-party workshops to address the need for standard methods for the performance evaluation of 3D imaging systems. The workshops were attended by manufacturers, users, and researchers from academia and government agencies from the U.S. and abroad. In 2006, ASTM committee E57 was established to develop standards for the performance evaluation of 3D imaging systems. The committee’s initial focus has been on standards for 3D imaging systems typically used for applications including, but not limited to, construction and maintenance, surveying, mapping and terrain characterization, manufacturing (e.g., aerospace, shipbuilding), transportation, mining, mobility, historic preservation, and forensics. ASTM E57 consists of four subcommittees: Terminology, Test Methods, Best Practices, and Data Interoperability.

Under the leadership of Alan Lytle, who leads the Construction Metrology and Automation Group at NIST, subcommittee chairs were chosen. These are:
• Gerry Cheok — Terminology (E57.01)
• Dave Ober — Test Methods (E57.02)
• Ted Knaak — Best Practices (E57.03)
• Gene Roe — Data Interoperability (E57.04)

Cheok is a research engineer at NIST; Ober has been with Metris, a global company that designs, develops and markets 3D hardware and software; Knaak is the president of Riegl USA; and Roe is with the Engineering and Construction Division at Autodesk.

According to Lytle, standards will accelerate the acceptance and use of 3D imaging systems in the construction, manufacturing, and transportation sectors, and will stimulate industry research and development in next-generation sensors. In the construction sector alone, it is estimated that the use of 3D imaging technology provides up to 5-10 percent savings of the total project through such means as rework reduction and schedule shortening. The goal is to make this productivity enhancing technology commonplace in the AEC industry.

Current Status of the Subcommittees
Even though the work of these subcommittees seems to me to be taking a long time, I’ve had numerous inquiries as to the status. So, I developed a questionnaire to find out. Each chair was asked the same questions, and here are their answers:

1 – Please explain the overall mission of E57 ASTM activities to the survey community:
Gerry Cheok — Terminology (E57.01) E57 is tasked with developing standards for 3D imaging systems. These standards will
• enable equitable evaluations of instruments so that users can understand how an instrument will perform 
• determine the tradeoff between performance and cost 
• provide uniformity in instrument specifications 
• facilitate data transfer between software applications and hardware  • improve product quality by providing guidance on best practices  • • • increase the confidence in the use of 3D imaging systems

Dave Ober — Test Methods (E57.02) This can be best answered by presenting the Scope of E57 which is "The development of standards for 3D imaging systems, which include, but are not limited to laser scanners (also known as LADAR or laser radars) and optical range cameras (also known as flash LADAR or 3D range camera)."

Ted Knaak — Best Practices (E57.03) E57 has an "official" mission statement, "The development of standards for 3D imaging systems, which include, but are not limited to laser scanners (also known as LADAR or laser radars) and optical range cameras (also known as flash LADAR or 3D range camera)." Personally, I see an implicit mission of E57 to define and educate the community as to the nature, characteristics and application of this very new and different technology.

Gene Roe — Data Interoperability (E57.04) E57 is focused on developing world class standards that will be used to guide and support the development of the rapidly growing and diverse 3D imaging industry.

2 – Please provide a mission statement that best describes the focus of your committee’s activities:
Gerry Cheok — Terminology (E57.01) The scope of E57.01 is "The development of terminology commonly used for 3D imaging systems."

Dave Ober — Test Methods (E57.02) Test Methods Scope: The development of standard protocols that will be used to characterize 3D Imaging System performance. Each protocol (or test method) includes setup, data collection, data analysis, and reporting as well as the hardware required to run each test. In addition, the environmental condition requirements and what is recorded in the final report is also part of the protocol.

Ted Knaak — Best Practices (E57.03) E57.03 defines the Best Practice as a process or method that, when executed effectively, leads to enhanced project performance. E57.03 shall develop, validate, document and communicate best practices in the successful and consistent application of 3D imaging technology. Using these practices and guidance, end users can specficy application requirements and associated deliverables traceable to accepted standards. Practitioners can determine instrumentation, procedures, and quality control processes yielding work product suited to application requirements.

Gene Roe — Data Interoperability (E57.04) To develop and promulgate open, standard data exchange mechanisms for 3D imaging system derived data in order to promote its widest possible use.

2a – Please provide a brief progress update:
Gerry Cheok — Terminology (E57.01) The subcommittee produced a standard, E2544 – Standard Terminology for Three-Dimensional (3D) Imaging Systems, in 2007. This standard contains two primary sections. One section contains terms that are relevant to the 3D imaging community but that have already been defined by other standards­these definitions have not been modified by E2544, just repeated. The other section, Section 3.2, contains terms specific to E2544 and to the 3D imaging community. Since 2007, the subcommittee has been adding new definitions to the standard. The current version of E2544 contains 21 terms in Section 3.2.
The major challenges that the subcommittee faces when developing definitions include: 
• ensuring that the definition applies to or encompasses all instances/ conditions/instruments to the extent possible. 
• harmonizing the terms across disciplines (the same terms often have different generally accepted definitions within different disciplines­ the challenge is to select or develop an appropriate definition that does not conflict with existing use or create ambiguity). 
• balancing simplicity and accuracy (technical correctness) of definition.

Dave Ober — Test Methods (E57.02) We are currently focused on developing a test method/protocol to characterize the performance of 3D scanning devices as a function
of increasing distance from the 3D scanner. While there are numerous other performance tests/protocols to be developed, we believe as a committee that this should be the first protocol that we complete. We have identified a framework for the protocol as well as reviewed numerous materials to identify a "fair" reflective first surface for the test artifacts. We are currently discussing the details of the measuring and setup.

Ted Knaak — Best Practices (E57.03) We have currently identified those areas of interest for development of Best Practices. We have submitted the "E57.03.003 Safety Standard" for general E57 review and acceptance. We plan to finish this standard at January 2009 meeting.

Gene Roe — Data Interoperability (E57.04) The subcommittee has been working on the development of a neutral binary data exchange format that will hopefully become an international industry standard. We hope to deliver a draft specification by early 2009, along with a reference, open source code implementation of a reader and writer.

3 – Please explain how your committee’s activities contributes to the overall mission of E57:
Gerry Cheok — Terminology (E57.01) A standard terminology will provide uniformity in instrument specifications and help users understand how an instrument will perform

Dave Ober — Test Methods (E57.02) The Test Methods subcommittee has the main task of developing the actual protocols against which all 3D scanning instruments and their performance evaluation will be measured. In the end, this subcommittee forms the basis for performance evaluation of 3D scanning devices. In addition, our committee must also incorporate the information from the other subcommittees (Terminology, Best Practices, and Interoperability) so that the test methods we develop are congruent with their work. For example, if the Best Practices subcommittee defines standards for Safety and Data Management, then our standard will need to make sure we incorporate them.

Ted Knaak — Best Practices (E57.03) Best practices focus primarily on the application of 3D imaging technology. E57.03 contributes to E57 by setting guidelines for "crossing the bridge" between technology and the successful application of that technology.

Gene Roe — Data Interoperability (E57.04) The beneficial growth of the 3D imaging industry is dependent on customers deriving value from the technology. Virtually every digital technology that has standardized on a data exchange format has seen tremendous growth and acceptance. Given the size issues associated with point cloud files it is even more important to solve this problem for customers.

4 – Please provide a clear example of how your activities will benefit the survey market in general as well as the individual user:
Gerry Cheok — Terminology (E57.01) 3D imaging systems are used in the construction industry in conjunction with standard survey instruments. Common terminology is critical to the 3D imaging and survey market and the individual user because it helps to reduce confusion and allows for fair comparison of instruments.
For example, the term resolution has different meanings to different people. Factors that influence resolution include beam width, object reflectivity, distance to the object, angle of incidence with the object, object material/texture, scan speed (for scanning systems), horizontal/ vertical orientation of the features relative to the beam direction. Therefore, without a standard definition and knowledge of the conditions under which this value was determined/measured, a user may arrive at an erroneous conclusion as to the instrument’s performance.
Other examples include: 
• the term accuracy has been used in the market place to mean error, noise, and resolution. Additionally, on specification sheets, accuracy has been specified as A1 mm, at A2 m to a A3 % reflective target for Instrument A and B1 mm, at B2 m to a B3 % reflective target for Instrument B where A2 and A3 are not equal to B2 and B3, respectively. As given, these specifications do not allow a user to compare instruments. 
• the term `spot size’ has been used to mean laser beam radius and laser beam diameter

Dave Ober — Test Methods (E57.02) This answer is based on why standards exist in the first place. To list a few: 
• Efficient capital equipment spending; "getting the right tool for the job" 
• Lowers barrier to adopting new technology by providing "expert" information and specifications
• Improves competitiveness /technology of the industry by driving improvements on meaningful metrological characteristics 
• Provides clear conditions for post purchase warranty issues 
• Lower capital costs by creating competition through comparison between instruments on specifications

Ted Knaak — Best Practices (E57.03) By providing best practices in the application of 3D Imaging technology, we will provide a common framework facilitating communication between service provider and customer. This shared understanding of the guidelines necessary to assure a project’s success will prove a key stimulus to technology adoption in the market.

Gene Roe — Data Interoperability (E57.04) The 3D imaging hardware and software vendors will have access to free software to develop readers and writers of the standard format. Customers in turn will not have to be concerned with proprietary data formats.

What All This Means
In a September 2006 article in ASTM Standardization News, Cheok and Lytle said, "Standard test methods for the performance evaluation of 3D imaging systems will provide a basis for fair comparisons, reduce the confusion regarding terminology, and increase user confidence in the applications of these systems. Best practices will improve product quality and will ensure a minimum level of performance."

As we move farther and farther into the use of laser scanners as another tool in our toolbox, standards and specifications, like the familiar DIN spec for angular accuracy, will allow not only allow equipment buyers, but also data consumers, to make informed choices. Hats off to these volunteers who are dedicating their time and expertise to accomplish this goal.

Marc Cheves is Editor of the magazine.

A 700Kb PDF of this article as it appeared in the magazine—complete with images—is available by clicking HERE