# Augmented Reality in Precision Farming: Concepts and Applications
## 3 Deployment Models
### Integrated Technology Frameworks  
The accessibility of AR-capable hardware enables mobile applications, known as Mobile Augmented Reality (MAR) [3]. As its name suggests, MAR offers the user the possibility of integrating virtual information into the physical real environment through a mobile terminal. In other words, the user is not limited to a particular location in order to utilise these systems. Specific aspects of a MAR framework will naturally depend on the purpose of the application. However, some general key aspects of such applications can be identified as suggested by [3, 12]. The former describes general foundations of MAR applications regardless of their application domain. The latter aimed to create a MAR framework specific for the agricultural domain.  
Specifically, [PERSON] et al., propose a framework consisting of four main aspects as depicted in Figure 5, namely (1) Physical layer, (2) Network layer, (3) Decision layer and (4) Application layer. The physical layer is the base of the application. It determines the characteristics of the whole architecture, as it sets the premise for the type of data that is available (or will be available) through the collection process.  
In the reviewed examples in Section 2, the physical layer is represented by all the primary sensors that collect and store relevant information for each application. For example, this could be a wireless sensor network (WSN) that collects site condition information for vineyard monitoring [26], databases containing crop diseases information [31] or information relevant to animal husbandry [16] and mission planer system data relevant to agricultural machines [15]. In short, this layer contains the information that will be used for decision-making.  
The Network layer enables access and transfer of information in the system. Technologies enabling this transfer include GPRS, microwave and satellite communication [12], wi-fi [13, 16, 31] and Bluetooth [16]. The last two layers, Decision and Application, are better explained jointly as the former, is the direct (visual) result from the latter. For example, in the application built by [PERSON] et al., the decision layer is represented by the functions _locate:cow_ and _display:cow_, which are triggered by clicking on a cow within the camera view of the mobile device. Similarly, the application presented by [PERSON] et al. [26], displays alerts, management information and geotagging of a specific plant/vineyard (Decision layer) following the interaction between the farmer and the device (Application layer); where the interaction between the user and the application calls from the Application layer.  
All the reviewed applications can be expressed by means of this framework. To name one example, [PERSON] et al., [16] developed a MAR application in which farmers use smart glasses to scan QR codes attached to a specific animal (application layer). Thereafter, retrieving information from databases and sensors relevant to animal husbandry (physical layer) through a combination of Wi-Fi and Bluetooth system (Network layer). Finally,  
Figure 4: (a) Mirror-based AR with Controllers, (b) AR with Controllers and no Mirror.  
the information is displayed as augmented features in the form of videos and a farm information sheet (decision layer) of the selected animal.