## 3 IoT Standards and Protocols for Precision Agriculture
### OGC SensorThings for Precision Agriculture (RQ3)  
To implement an interoperable architecture for precision agriculture, the OGC SensorThings standard was selected. In addition to meeting all the requirements (listed in Table 4) for developing an IoT platform for precision agriculture, it also possesses the four following features that make it ideal for creating an interoperable architecture.  
**Object Modelling**: The OGC SensorThings standard ensures that all objects are modelled in the same way: every object described with the OGC SensorThings standard possesses the same types of entities and properties, facilitating the standardization of data received from sensors. Specifically, the device responsible for \"translating\" the data does not need to assign a specific code or tag to each object or property but is free to model any object using the structure provided by the OGC SensorThings standard without the risk of having outdated or incomplete information.  
**Geolocation**: Another advantage of using the SensorThings standard is its handling of geolocation; unlike the other standards analysed, where the position of the device is expressed through a property of the object, OGC SensorThings manages the geolocation of objects natively. Specifically, while with other standards the location history of objects must be managed externally by extracting positions from various properties, SensorThings automatically collects all positions occupied by devices and stores them in an \"entity\" called HISTORICAL LOCATION whenever the geographic location of a device changes.  
\begin{table}
\begin{tabular}{l c c c c c} \hline \hline
**Requirement** & **SigFox** & **NB-IoT** & **LoRaWAN** & **WiFi** & **Bluetooth** \\ \hline
**Lightweight Data Flow** & ✓ & ✓ & ✓ & & \\ \hline
**Simplicity** & ✓ & & ✓ & & ✓ \\ \hline
**Easily adaptable** & & ✓ & ✓ & ✓ & ✓ \\ \hline
**Open Platform** & & & ✓ & & \\ \hline
**Geolocation** & ✓ & ✓ & ✓ & & \\ \hline
**Support various data types** & & ✓ & & ✓ & \\ \hline
**Open Source** & & & ✓ & & \\ \hline
**Precision Agri. Needs** & & ✓ & ✓ & & \\ \hline \hline \end{tabular}
\end{table}
Table 8: Comparison of IoT protocols based on precision agriculture requirements  
**Date and Time**: Another key feature for selecting the OGC SensorThings standard is its native support for managing date and time. Every observation made by the device and every reported position includes a property that contains the timestamp of the measurement. If the sensor does not send the date and time of the measurement, it is the responsibility of the receiving server to provide them, as specified by the standard.  
In the field of precision agriculture, it is crucial to know the exact time of day when a measurement is taken for accurate analysis, especially when it is necessary to cross-reference data to determine the position of the sensor at the time of the observation.  
**Ease of Use**: The final factor that influenced the choice of the OGC SensorThings standard is its ease of use. The standard's specifications are clear and intuitive, with various entities and properties named in a way that makes their purpose easily understandable. Additionally, there is no need to memorize large amounts of data or codes for its implementation. This feature is especially important during the installation phase, when part of the data must be initialized in the database and entered manually. This task is usually performed by users who may not have in-depth knowledge of IoT standards.