IEEE Systems, Man, and Cybernetics Magazine - January 2018 - 23

Within this continuum, AR describes an environment
where the physical world is enhanced by adding computergenerated objects using computer-vision methods to make
them appear as if they coexist in the same dimension [24].
Therefore, AR supplements reality rather than completely
replacing it. AR displays useful information that is not
directly detected by the senses, helping users to perform
real-world tasks and facilitating their understanding of
complex scenarios [25]. Its potential relies on the possibility of enhancing reality and making invisible things
visible [24]. Azuma et al. identified three main technologies that support AR systems, which can be considered for
any MR system in general [25]:
1) Interaction technologies. These enable the user to manipulate virtual elements in real time. They include the use of
tangible interfaces, such as touch screens and haptic
devices, and natural interaction interfaces, such as gesture
and speech recognition.
2) Display technologies. These allow the positioning of
real-world elements with computer-generated objects
and information, superimposing them on the user's field
of view. These technologies can be classified as wearable technology (e.g., head-mounted displays and smart
glasses), handheld displays (e.g., mobile devices like tablets and smartphones), and fixed projective displays
(e.g., stationary screens and caves) [8], [26]. While fixed
projective displays do not offer the immersive experience of wearable devices or the portability of handheld
displays, they are a low-cost alternative.
3) Tracking technologies. These methods make possible
the illusion of a true blend between virtual elements and
the real world. For example, in a transparent AR display,
it is very easy for the human eye to perceive any mismatch between real objects and virtual graphics, dashing the illusion of coexistence [27]. Accuracy in matching,
therefore, is quite important. Tracking is the activity of
locating the user's position and orientation in reference
to an environment [28]. It is generally based on two
approaches: 1) the use of computer-vision techniques
and 2) the use sensor devices. AR tracking, however, has
moved from simple marker-based systems to naturalfeature tracking and hybrid sensor-based methods [27].
Within sensor tracking, it is possible to identify two
main scenarios:
* Outdoor tracking is generally based on global positioning system (GPS) hardware, which is used to provide location over a wide area. The GPS is a navigation
system based on satellite information, owned and
maintained by the U.S. government, and accessible to
anyone with a GPS receiver. The GPS's accuracy
depends on multiple factors, including atmospheric
effects, sky blockage, and receiver quality [29].
* Indoor tracking uses inertial-motion devices, such
as accelerometers and gyroscopes, which are available in mobile and wearable devices. Inertial tracking is faster and more robust when rapid changes

MR
Reality
Real
World

Virtuality
AR

Augmented
Virtuality

Virtual
World

Figure 1. The MR continuum [23].

occur compared to vision-based tracking methods
[30]. A downside of inertial trackers is that they tend
to drift due to noise accumulation.
Furthermore, errors in tracking systems can be present
because of the different levels of accuracy among sensors
associated with dynamic environments, which are
affected by environmental noise and sensor wear and
tear. A common approach to overcome these issues is the
fusion of multiple devices to increase the accuracy of the
tracking and minimize its errors.
As Weiser predicted, technology is gradually disappearing from our consciousness as it becomes integrated
in our everyday lives [15]. Immersive technologies have
become more pervasive, thanks to mobile and wearable
devices, generating large amounts of contextual information. This creates the opportunity to implement artificial
mechanisms for accurate context representation, including for adaptation and learning.
Intelligent Immersive Systems
for Service Operations
As previously described, Service 4.0 aims to support and
promote innovation in service operations for organizations
using emergent technologies. Service can be understood as
economic activities that satisfy consumers' needs but produce no tangible goods [31]. From this perspective, several
challenges can be identified:
◆ the increasing complexity of automatized technology
components, which can include multiple distributed,
configurable components, adding complexity to operational systems
◆ workers' increased mobility, particularly for service
operations, in which staff members usually need to
travel to different locations for maintenance and supply tasks
◆ high uncertainty levels present in real-world applications due to diverse factors, such as the environment
and human behavior.
To meet these challenges, we should consider mobile,
context-aware systems to provide users with relevant
information and services retrieved from companies' databases, tailoring their application through gathered contextual information. Context could be defined as any
information that can be used to characterize an entity's situation, an entity being a person, place, or object that is
considered relevant to the interaction between a user and
an application, including the user and the application itself
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Table of Contents for the Digital Edition of IEEE Systems, Man, and Cybernetics Magazine - January 2018