The iHelmet: An AR-enhanced Wearable Display for BIM Information - Mobile and Pervasive Computing in Construction - page 159

Figure 8.6 Procedure for positioning

Distance Value

As shown in Figure 8.7, the format of the distance value is a direction sign plus a
distance value. The direction sign will automatically change according to the user's
position. For vertical distance, if the user's position is closer to the north side of the
view unit, the sign will be N, whereas the sign will be S when the user is closer to
the south side. For horizontal distance, if the user's position is closer to the east side,
the sign will be E, whereas the sign will be W when closer to the west side. To
calculate the distance, it is first necessary to calculate the proportion (P S ) of the
screen's dimension in pixel to unit length, to get the dimensions of the area plan in
supposedly millimeter units as shown in Equation 8.1:

P S ¼ S P = S i ð 8 : 1 Þ

Figure 8.7 Two instructions: distance value and projection range