Augmented Reality – AR is in the center of scientific interest as it blends the real world with additional digital content to enhance the user experience and create more immersive solutions. In this article we will walk through the development of an AR application for mobile devices which utilizes Cloud functionalities to share cross platform AR experiences while using cross platform development tools featuring a single codebase for both mobile operating systems (Android, iOS).
Augmented Reality
Mobile AR’s importance lies in its ability to transform our experience with the real world through smartphones. By overlaying digital information onto physical objects, mobile AR unlocks a new way to learn, shop, and interact with everyday surroundings. This wide accessibility, thanks to existing devices, makes it a powerful tool for businesses and a game-changer for how we perceive and interact with the world around us.
An important term in AR terminology is the AR Anchors which act like digital tethers in the real world. Imagine pointing your phone’s camera at a spot on the floor and placing a virtual object there. An AR anchor remembers that specific location and ensures the virtual object stays put, even as you move around. This keeps the virtual world aligned with the real one, creating an immersive AR experience.

(Source: Google AR Core)
Cloud AR is the missing piece that unlocks the full potential of mobile AR. Imagine a world where AR experiences aren’t limited to your device but persist in the environment itself. Cloud AR acts as a shared brain for AR, storing and processing data to create persistent, multi-user experiences. This paves the way for groundbreaking applications across fields like education, collaboration, and navigation, ultimately transforming how we interact with the physical world through technology.

(Source: Google AR Core)
Anchor Placement functionalities
To better understand the flow of Cloud AR applications we need to define two AR functionalities: the Anchor Placement flow and the Anchor Resolving flow. In the Placement flow we will start a cloud-enabled AR session (using one of the Cloud AR development libraries: Unity AR Foundation, ARCore, ARKit, Vuforia) and perform a good scan of the area. Then, after selecting a position for attaching our Anchor, we will perform the upload process of this Anchor. In the Resolving flow we will use the Anchor IDs that were generated by the upload Anchor process to resolve the anchors by a different device looking at the same place.
Anchor vs Anchor Content
As described earlier, Anchors are positions in the real world which are able to attach virtual content to. It needs to be clear though that Anchors are different entities from their content. The data model of an Anchor contains (apart from the Anchor Point Cloud that localizes itself in the frontal scene) the coordinates of the Anchor in the current AR Session. This is different from the content that is displayed to the user. The Anchor contains only information about the Location at the scene.

Anchor as Point of Interest
The aforementioned comparison suggests that an AR Cloud Anchor can function as a point of interest capable of displaying various dynamic content. This content can not only vary depending on the user, but its relative location can also differ. For example, an AR Cloud Anchor could be placed at the center of the room, while the Anchor Content could be displayed one meter to the right relative to the AR Cloud Anchor’s position. Furthermore, multiple items (such as 3D models) can be attached based on the position of a single Cloud Anchor and oriented in relation to that Anchor.
This process has the benefits of requiring only one Anchor to be placed and then resolved, resulting not only in faster resolving times but also in decreased processing power and, hence, decreased battery consumption, decreased network data traffic and simpler maintenance by the system administrators.
A living example of the proposed Architecture: The euPOLIS Prototype Application
The Point of Interest Architecture was initially applied to the development of a prototype application for the euPOLIS Project. This Nature Based Solution has the goal of motivating the citizens to increase their physical activity by monitoring them through wearables and prompting them to visit specially developed smart pocket-parks across various cities of the EU.

The prototype application provides the park visitors with information about their recorded physical activity, such as activity Leaderboards and Badges (compared to other visitors). Moreover, weather information (temperature, humidity) at the site is also presented along with indications for various park attractions. These valuable illustrations are displayed to the user as 3D AR Content at predefined locations utilizing AR Cloud Anchors and following the Point of Interest Architecture.


An example of the 3D AR Content during the development phase of the prototype. The prototype development process was included in the proceedings of the EHPWAS Workshop and presented at the WiMOB Conference in 2022 at Thessaloniki, Greece.
Conclusion
Mobile Augmented Reality (AR) empowers developers to craft captivating experiences that seamlessly transcend device boundaries (across various platforms). However, the organization of AR entities, data, and models plays a pivotal role in determining the success and functionality of an AR application. This article proposes a novel Cloud Augmented Reality Architecture that addresses the challenge of managing multiple AR Cloud Anchors within a single environment. By resolving only one Cloud Anchor and programmatically displaying a vast amount of related AR content, this architecture streamlines the development process and enhances user experience.
Scientific References:
Koulouris, Dionysios, Andreas Menychtas, and Ilias Maglogiannis. “Augmented Reality for Indoor Localization and Navigation: The Case of UNIPI AR Experience.” International Conference on Computer Analysis of Images and Patterns. Cham: Springer Nature Switzerland, 2023.
Koulouris, Dionysios, et al. “Utilizing AR and Hybrid Cloud-Edge Platforms for Improving Accessibility in Exhibition Areas.” IFIP International Conference on Artificial Intelligence Applications and Innovations. Cham: Springer Nature Switzerland, 2023.
Koulouris, Dionysios, et al. “Integrating AR and IoT services into mHealth applications for promoting wellbeing.” 2022 18th International Conference on Wireless and Mobile Computing, Networking and Communications (WiMob). IEEE, 2022.