Civil Engineering Reference
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Figure 6.2 Outdoor hardware prototype using GPS to determine position
iron correction algorithms to calibrate out magnetic anomalies for repeatable,
high resolution measurement in challenging environments. The tracking device
was placed at the highest point inside the user's helmet, directly above the top of
the head, and parallel to the forward line of sight (Figure 6.2). The GPS measures
the user's position as longitude (
x
), latitude (
y
), and altitude (
z)
. The magnetic
tracker, on the other hand, measures the orientation of the user's head (and thus
line of sight) in the form of yaw (
a
), pitch (
b
), and roll (
g
)angles.Thesesix
measurements fully define the user's outdoor location and line of sight at any
given time.
However, GPS technology is not suitable for indoor applications because it
becomes ineffective when there is no continuous straight signal path between the
satellites and a receiver. Therefore, other feasible techniques of user position and
orientation tracking in indoor enclosed environments had to be investigated. The
authors therefore explored the applicability of wireless technologies, namely
Wireless Local Area Networks (WLAN), Ultra-Wide Band (UWB), and Indoor
GPS for dynamic user position tracking in situations where GPS is unavailable. The
same orientation device was used indoors. By tagging users with appropriate
receivers/tags and deploying a number of nodes (access points, receivers, trans-
mitters, etc.) at fixed positions indoors, the location of tagged users can concep-
tually be determined and continuously tracked.
The objective of the following sections is to describe three key wireless tech-
nologies applicable for indoor positioning, portray and compare the technical
characteristics of these technologies, and highlight the extent to which each
technology can be used to accurately calculate the positional context of a user
in congested dynamic environments, such as those found on construction sites.
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