Ubiquitous User Localization for Pervasive Context-Aware Construction Applications - Mobile and Pervasive Computing in Construction - page 102

Figure 6.12 Multilateration approach

“ is a Virtual Group ID. The tag location data is computed from the time of

flight measurements of the receivers within the virtual group.

Unit ”

“ ”

LF is a Line Feed

character (with ASCII code 0x0A), to terminate a location data string. Among all

the output information, the “Data Header”, “tag#” and “X, Y, Z” are of primary
importance for the purpose of this research.
Similarly to the WLAN-based tracking application, location information (X, Y,
Z) was extracted from one positioning technology, UWB, and then combined with
the orientation information (roll, yaw, and pitch) received from the tracker within
the same application. TCP sockets were used to connect directly to the Hub and
provide a quick and effective way for accessing location information from a local
computer/laptop. This was achieved by opening a socket connection given the IP
address of the hub and the port number, reading values (Figure 6.13a) according to
the Sapphire output format and then performing a string manipulation on the
values extracted to obtain the x, y, and z coordinates (Figure 6.13b). Only values
corresponding to a tag header

¼

were extracted (n1, n2, and n3). The positioning
values were then used together with orientation values received from the magnetic
tracker and integrated in one application to retrieve tracking information
(Figure 6.14).

R

6.3.3 Indoor GPS-based user position tracking

Indoor GPS (Metris Products, 2007) is the third tracking system studied in this
research. The system is mainly defined by transmitters and receivers (Figure 6.15).
A battery operated transmitter uses laser and infrared light to transmit one-way