Practical Advantages of a Universal Geometry Measurement Method

Charles J. Lloyd
Visual Performance, LLC
St. Louis, Missouri

From the Proceedings of the 2017 IMAGE Society Annual Conference, Dayton, Ohio.


Within the simulation training industry customers and suppliers of muti-channel display systems spend significant time and dollars dealing with geometry measurements. For the typical training display system, customers often impose distinct requirements for absolute geometry, relative geometry, and the geometric co-alignment of dots in the blend regions between channels. Today acceptance testing is typically performed using a manually-aimed theodolite and a spreadsheet running on a portable computer. Using current methods the complete measurement of system geometry requires at least several hours and may require more than one shift for a many-channel display system. Additionally, significant time is required to develop and install a system-specific test pattern with extra dots in the blend regions between channels and to prepare a custom spreadsheet that computes metrics based on the specific organization of channels and blends.

In this paper we describe a new approach to system geometry measurements that significantly reduces the complexity and substantially decrease the time required to make these measurements. While proprietary automated geometry measurement systems have been available from multiple suppliers in the simulation training industry for more than a decade, these systems are not used for acceptance testing because: 1) they are not installed at the eyepoint(s) of the display system; 2) they are not calibrated independently of the display system; and 3) there is little standardization across the suppliers of these automated measurement systems.

The proposed method calls for a universal test pattern containing one alignment dot per square degree that covers an entire sphere. Since the sphere covers any possible configuration of windows (channels), the same pattern can be used in any display system. The dots in the pattern are color coded to enable automatic identification of the dots without additional geometry landmarks or labels. Automated measurement systems with typical cameras can simultaneously measure thousands of dots per image for a data collection rates far exceeding current methods.

With the goal of developing industry standard practices, we are publishing the Metric definitions, Test pattern description, and measurement Procedure (MTP) and soliciting stakeholder feedback so that the method can be improved. The use of vetted and published standard measurement procedures is expected to improve consistency from one program to the next and to reduce the complexity of preparing requirements and test plans. The use of stable, objective, and unambiguous requirements and measurement procedures is expected to reduce the risk to suppliers who wish to avoid discrepancies and delays during acceptance testing.