**8. Augmented reality location**

Each of indoor and outdoor sites offered many of similar challenges that must be processed to successfully implement AR systems, such as content acquisition [11], content storage and categorisation [46], tracking and calibration [47], marker placement, usability [48] and ergonomic issues [49]. Hence, there are various issues that must be taken into account in order to overcome by special internal or external sites.

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**Figure 6.**

*Augmented reality for outdoor heritage.*

*Cultural Heritage in Marker-Less Augmented Reality: A Survey*

AR's previous applications for indoor cultural heritage sites have frequently taken the form of "virtual museums". The visitors use AR technology to display objects that may not be accessible to them. This is because the great value or fragility of such objects, or the lack of space inside the museum or the physical object is existing in another museum [36]. One of the main issues that affect the design of AR systems for indoor sites are those of marker placement if using marker-based tracking, as well as ensuring the optimal use of the systems for all age groups and levels of computer literacy. In addition, it is substantial to make sure that hardware used is strong enough in order to support AR applications, and it is structurally

It can be said that the development of AR systems for outdoor applications is more difficult than indoor applications. Realistic historical buildings in outdoor rendering AR systems require advanced effects such as shadows, lighting and the ability to detect the impact of sky dome illumination on virtual in addition to the real objects [23]. The environment and resources, such as lighting conditions and electrical energy, cannot be as tightly controlled, as well as hardware cannot normally be left outdoors. The use of mobile computer systems in outdoor AR generates several problems such as it is uncomfortable and heavy to wear, and it is very expensive if it is a wearable system combined with an HMD [11] Outdoor AR is a technology of executing augmented reality using outdoor GPS, compass, gyroscope sensor based on augmented reality technology. Unlike to indoor AR, outdoor AR is not subject to spatial restrictions. Indoor AR used a marker to ensure suitable synthesis of virtual object because it happens in relative narrow space, while outdoor AR used location information; it does not use any marker like in indoor system because it happens in relatively wide area [50]. Often the lack of ideal conditions means that marker-based tracking systems cannot be used, leading to rely on other

techniques, for example, GPS and inertial sensors, which can be inexact.

concentrated on outdoor, indoor, reconstruction and realism.

One of the key problems that faced to design AR systems for outdoor sites are effectively tracking without using of markers in an environment that may be devoid of features in order to use for tracking. In addition, ensuring that any device used is weather-resistant and vandal-resistant. Furthermore, all the hard-wires that are used must be powerful enough to support AR applications, as with indoor sites. **Figure 6** shows the AR for outdoor cultural heritage **Table 1** shows a comparison between investigated works in AR systems,

**8.1 Augmented reality for indoor heritage sites**

**8.2 Augmented reality for outdoor heritage sites**

*DOI: http://dx.doi.org/10.5772/intechopen.80975*

robust if being lent to the public.
