Electronic 3-D Scans
The Cyberware WB4 whole body scanner will be used in the CAESAR project to generate the high-resolution data of the human body's surface. The whole body digital images created from these scans include color and range data. Each subject will be scanned in three postures.
The scanner has four scanning heads that project a horizontal laser line on the scanned subject. Subjects can sit or stand on a round platform mounted on the scanner frame. The scanner heads "see" a cylindrical area 2 meters high and 1.2 meters wide (roughly the diameter of the platform on which the subject is positioned). The subject's entire body is scanned within 17 seconds. When the scan is complete, the digitized images are "zippered." Zippering is a process that merges the four raw data files produced by each scanning head.
Several types of files are created from the Cyberware scanner and the Cypie merging software. The Cyberware scanner produces two unzippered or raw data files for each scanning head; they contain the range and color information. The Cypie software creates the zippered file (cg07a.ply, for example) by merging the color and range data files from the unzippered files. One merged file is about 9 megabytes of data in binary format and approximately 40 megabytes in an ASCII type form. The zippered files will be provided as deliverables on some form of magnetic media such as a compact disc.
The scanning procedures used for the study include dressing the subject in standardized clothing, placing landmark markers, and positioning the subject on the scanning platform. The standard scanning apparel for both men and women includes light-gray cotton biker shorts, and a gray sports bra for women. Latex caps will be used to cover the hair and provide a more accurate shape of the head.
To understand the data user's needs, a list of 99 variables were compiled through meetings with representatives from the military, automotive, clothing, and aerospace industries. In developing the procedures, an effort was made to ensure the ability to extract these measures.
CARD Lab researchers initially used 99 anthropometric variables to determine how much of this information was provided by various subject postures to select the best assortment of positions. Two of the three postures proposed for scanning are the standing posture and the sitting posture as in traditional anthropometric measurement. Standardized scanning postures must meet several requirements:
• Provide accurate comparisons to traditional anthropometric variables.
• Be reproducible, so subjects are always scanned the same way.
• Maximize the body surface coverage of the scan.
• Reveal all anthropometric body markers to ensure the markers are visible in the scan.
Traditional anthropometric sitting and standing postures are highly reproducible. However, several scanner limitations inhibit their effectiveness for 3-D scanning. For example, a traditional anthropometric standing posture requires the subject to hold the arms at the sides with the legs and ankles together.
In this position it is impossible for the scanner to see highly shaded areas under the arms and between the legs. In addition, landmarks like the medial humeral epicondyles (inner side of the knee) and the medial malleolus (inner side of the ankle) are hidden. Abduction of the arms and legs (holding them away from the body) allow the scanner to "see" the undersides of the arms and legs.
The proposed standing and sitting postures for the CAESAR project are similar to the traditional postures for whole body scans with some abduction of the arms and legs:
The standard anthropometric sitting posture requires that the arms and legs form right angles at the elbow and knee joints. In this posture the subject's thighs and forearms are in the horizontal plane. Because the scanner projects laser light in a horizontal plane, horizontal surfaces do not reflect light back to the scanning head. Without this information, it is difficult to measure thigh clearance or forearm circumference.
To resolve this dilemma, CARD researchers plan an additional seated scanning posture that maximizes body surface coverage and marker visibility:
This posture lowers the foot position to increase the knee angle. As a result, the thigh is no longer horizontal and can be seen by the cameras. The hands are held over the head in the midsagittal plane in what one subject called "the stick-em-up position." Shading is eliminated, and this arm position is easily reproducible because of the right angle at the shoulder and elbow. Hard-to-see landmarks like the iliocristale (side of the hip) and medial humeral epicondyle (inner side of the elbow) are easily visible.
