# A Low-Cost IoT-Based System to Monitor the Location of a Whole Herd
## 1 Introduction  
Animal location and tracking have been topics of interest for both wildlife and livestock researchers for a long time. Animal location recording allows researchers to evaluate some key aspects, such as the movements of animals around the landscape [1], the spatial heterogeneity of field occupancy by animals [2], the pasture utilization, the animal performance and behavior [3], or the social affiliations within a herd [4, 5]. Early methods for animal location relied on human observation of natural (color patterns) or artificial features (colored collar or tag). Problems of these methods included observer fatigue and associated error, physical limitations, external factors (weather and light), and the effect of observer proximity on animal behavior [3]. Since the late 1950s, very high frequency (VHF) tracking technologies have been commercially available to gather location data [6]. However, VHF-based tracking systems also have several limitations, from, e.g., disturbing the animal to only being able to track during theday because of the difficulty of the terrain. Location fixes and accuracy depend on the position of the researcher (ground or air), his discomfort and fatigue, his visibility, and the characteristics of the terrain. Without a visual sighting, errors may exceed 500 m [6]. Commercial development of telemetry systems based on global positioning systems (GPS) began in 1991, offering researchers the opportunity to overcome most of the limitations listed above. GPS-based systems have the potential to collect large amounts of high-quality location data 24 h per day and under all weather conditions. The accuracy of GPS tracking systems is generally considered to range from 5-30 m [7; 8], depending on vegetation cover, topography and even animal position [9]. Thus, a new era of animal tracking began after the commercialization of GPS-based systems, and scientific literature contains numerous examples of successful studies using GPS positioning [10; 11; 12]. The first GPS animal units were fitted with a 400 g lithium battery pack that was expected to provide one year of operation at eight fix attempts per day, although field trials downgraded life expectancies to provide 268 days of service at six fixes per day [13]. The total weight of these first units was 1.8 kg, which limited their use to research studies on large mammals. Due to advances in the miniaturization of sensor technologies and to the development of higher energy-dense batteries, some devices enabling the tracking of smaller species, e.g., birds, are now available [14]. Nonetheless, even with current devices, the size of the battery pack is critical in finding a threshold between the temporal resolution and the operational life. Another important drawback of most early GPS-based systems was that data were stored on board until the unit could be remotely released by a radio-activated \"break-away\" mechanism or recovered by the recapture of the animal. The development of mobile communications has enabled the transfer and regular updating of location data by GSM/SMS or GSM/GPRS services [15]. GSM services are widely available in Europe, but there are many vast areas throughout the world, mostly rural areas, without them. Opportunistic sensor networks, based on peer-to-peer routing, have been used to gather location data of several animals when GSM services were not available [16]. However, regular updating of the information can be challenging in that case. The Internet of Things (IoT) is a paradigm shift in the enhancement of the connectivity of the Internet. It provides the technical feasibility for a large number of sensors, actuators, and smart devices to remain connected with it, which is key for the development of real-time or quasi-real-time applications. The requirements of IoT applications have driven the emergence of low power wide area (LPWA) networks. They provide long-range communication up to 10-40 km in rural areas and 1-5 km in urban areas.