# Smart Sensors and Smart Data for Precision Agriculture: A Review
## 2 Types of Smart Sensors in Precision Agriculture  
Today's smart sensors are fundamental to data-driven decision-making in PA, facilitating farmers' monitoring and optimization of various parameters vital to crop health and resource management. As mentioned in [53], agriculture relies on six key sensors, particularly in outdoor farming. These sensors include location and position sensors, essential for precise field operations; optical sensors, which measure soil properties at different light wavelengths; electrochemical sensors, providing information on soil pH and nutrient levels; mechanical sensors, offering information on soil compaction; dielectric/electromagnetic soil moisture sensors, determining soil moisture levels; and airflow sensors, measuring soil air permeability. In addition, the importance of Photosynthetically Active Radiation  
Figure 5: Annual publications of papers indexed in Web of Science by different Sustainable Development Goals during the period 2018–2023. (PAR) sensors in optimizing plant growth conditions is discussed, as is the presentation of robotic sensors for crop weeding and spraying as effective and environmentally friendly alternatives to the traditional use of pesticides. This section gives an overview of the diverse range of intelligent sensors that have become indispensable tools in modern agriculture. Generally, wireless communication technologies classified according to transmission distance can be divided into three categories: short-range (\(\leq\)10 m), medium-range (10 m to 100 m), and long-range (\(\geq\)100 m). Short-range technologies discussed include RFID, Bluetooth, and UWB (Ultra-Wide Band); each of these technologies is specifically designed for applications with limited proximity [54]. Wi-Fi and ZigBee are identified as major players in medium-range wireless communication technologies, offering reliable performance within a range of 10 to 100 m. The focus then shifts to long-range wireless communication technologies, in particular LPWA (Low-Power Wide-Area) options such as LoRa, NB-IoT, and Sigfox, which have emerged as alternatives to traditional cellular networks (2G/3G/4G/5G) [55]. LPWA technologies are characterized by low energy consumption, low data rates, wide coverage, and support for massive connections. Although LPWA technologies are not suitable for streaming audio or video data, they excel at connecting devices requiring minimal data transmission over long distances with extended battery life [56]. Figure 6 illustrates a comparison of range and speed among different wireless communication technologies. In terms of comparative analysis, it highlights the trade-offs between power consumption, communication range, and data throughput for various wireless communication technologies. Notably, Bluetooth is identified as optimal for low power consumption, while ZigBee offers balanced range and data throughput [57]. LPWA technologies, such as LoRa and NB-IoT, are recommended for applications favoring long-range communications and low power consumption, even at the expense of lower data rates [58]. This comprehensive overview helps to understand the strengths and limitations of different wireless communication technologies, providing valuable information for a variety of applications. Table 2 shows a comparison of existing communication technologies along with their limitations. Figure 6: Range and rate comparisons among wireless communication technologies. -Weather and Environmental Sensors  
In the field, weather and environmental sensors provide real-time data on weather conditions, including temperature, humidity, wind speed, and precipitation. These sensors also measure environmental parameters such as atmospheric pressure and solar radiation. They are essential for forecasting and managing weather-related risks, optimizing irrigation, and ensuring the general well-being of crops. The application of wireless sensor networks in greenhouses offers significant advances in crop management.