OTCdoc, thank you for posting those reads. In the article pertaining to the drones, I saw no mention of a 3D Volumetric Display, or any other display of any type, or technolgies incorporated into the display itself. The drones, "collect stereoscopic 3D imagery."
Stereoscopy (also called stereoscopics or 3D imaging) is a technique for creating or enhancing the illusion of depth in an image by means of stereopsis for binocular vision, and the core process dates back pre 1868.
As far as Zebra's sand table display, that is a flat surface 3D display, that is full parallax, sub catergory light feild display. 3DIcon is working on technology to create a true 3D volumetric display (no illusions) -apples and oranges in the realm.