The iHelmet: An AR-enhanced Wearable Display for BIM Information - Mobile and Pervasive Computing in Construction - page 162

Single Tap

A single tap was used to select a floor, select a view unit, and lock/unlock the view
unit. Tapping the upper right portion of the screen selects upper floors, and
tapping the bottom right portion of the screen selects lower floors. Selecting a
view unit is through tapping and dragging across the screen. After a view unit is
selected, tapping the upper side of the screen locks the view unit, to avoid any
accidental taps by the user. If users want to select another view unit, tapping on
the lower side of the screen unlocks the view unit, allowing users to make another
selection.

Slide

A slide control was used to enter the next view or return to the previous view. Once
users have selected a floor or a view unit, they can enter the next view by sliding their
finger across the screen from left to right. Sliding across the screen from right to left
returns to the previous view, to select another floor or view unit.

Double Tap

Users can obtain detailed information by double tapping the screen. For example,
when viewing the rebar plans, double tapping on the screen shows information
about the rebar, such as the dimensions of the rebar (diameter, cut-off length, bend,
etc.) or the arrangement of the rebar. When viewing piping plans, double tapping
on the screen shows the dimensions and positions of the pipes or conduits. When
viewing the electrical plans, double tapping on the screen shows detailed infor-
mation about sockets and other inserts.

Gesture Control

An intuitive gesture control was developed to regulate the vertical range of the
information when projecting. According to the elevation angle of the user's head,
the information automatically changes to match the user's view range. As the user
looks up, the display changes to the information on the upper side. As the user looks
down, the display changes to the information on the lower side.

8.3.4 Display module

To provide users with more visualized and more realistic information, it was
proposed to use full-scale projections to display the information. Since different
positions have different scale ratios, to generate a full-scale projection, it is firstly
necessary to specify the user's position, as discussed in Section 8.3.2.
Secondly, the scale ratio of the projection (R P ) has to be calculated. The
Projector's Throw ratio R T (Distance/Width) can be obtained from the projector's
manual. From the capitalized ratio, we can calculate the scale ratio (R P ) can be
calculated as shown in Equation 8.3:

R P ¼ W P = W O ð 8 : 3 Þ