Here’s an article on IVAS with a discussion of ATAK from the Army Times. (This whole article is worth a read):
ONE DEVICE, MULTIPLE FUNCTIONS
IVAS is drawing on existing and developing Army programs to bring a host of functions and capabilities into one device.
The Android Tactical Assault Kit is a program that allows soldiers to use current military radios to swap information back and forth, from mapping items mentioned earlier to short text messages. Its main function is to provide situational awareness for troops.
It’s the backbone for the chat, location marking, mapping both from the cloud and stored formats, navigation and altitude data.