SIVT and IVAS are the same device. as this Tweet from 2021 shows. SIVT is a group effort, Soldiers working as a Team and IVAS will be the device they use in that effort. eMagin is building the Prototype Display for this purpose...

 

#FollowFriday: CSM Michael Crosby, Senior Enlisted leader of Army Futures Command, visiting with members of the Integrated Virtual Augmentation System (IVAS) and Squad Immersive Virtual Trainer (SIVT) team at the Soldier Integration Facility on 28 July 2021. [📷: @armyfutures] pic.twitter.com/hQ8rDDaclQ

— PEO Soldier (@PEOSoldier) October 15, 2021