  Immersive technologies offer new opportunities to support collaborative
visual data analysis by providing each collaborator a personal, high-resolution
view of a flexible shared visualisation space through a head mounted display.
However, most prior studies of collaborative immersive analytics have focused
on how groups interact with surface interfaces such as tabletops and wall
displays. This paper reports on a study in which teams of three co-located
participants are given flexible visualisation authoring tools to allow a great
deal of control in how they structure their shared workspace. They do so using
a prototype system we call FIESTA: the Free-roaming Immersive Environment to
Support Team-based Analysis. Unlike traditional visualisation tools, FIESTA
allows users to freely position authoring interfaces and visualisation
artefacts anywhere in the virtual environment, either on virtual surfaces or
suspended within the interaction space. Our participants solved visual
analytics tasks on a multivariate data set, doing so individually and
collaboratively by creating a large number of 2D and 3D visualisations. Their
behaviours suggest that the usage of surfaces is coupled with the type of
visualisation used, often using walls to organise 2D visualisations, but
positioning 3D visualisations in the space around them. Outside of
tightly-coupled collaboration, participants followed social protocols and did
not interact with visualisations that did not belong to them even if outside of
its owner's personal workspace.
