# A Low-Cost IoT-Based System to Monitor the Location of a Whole Herd
## Results
### System Validation in Commercial Farms
Nevertheless, this value is higher for sheep, meaning that an ewe has more chances to have other animals at a relatively short distance than a cow. On the other hand, the proportion of collar messages without BLE tag readings did not change significantly for the different collar/tag ratios (\(p>0.05\)). This indicator is lower for sheep, which can be interpreted as ewes being less likely to be separated from the rest of the herd than cows. Since the sampling scheme of the simulation process was done without replacement, the values for the case of 25 GPS collars correspond to the population mean and, therefore, the resulting standard deviation is zero. The charts included in Figure 4 represent the evolution of the number of messages coming from the GPS collars and the BLE tags over the 100-day duration of the experiment for different collar/tag ratios. They have been generated through the random iterative process explained in Section 2.3. Figure 4: Evolution of the number of messages received daily from GPS collars (orange lines) and BLE tags (blue lines) over the experiment: (**a**) messages from the sheep farm with five collars and 25 tags; (**b**) messages from the beef cattle farm with five collars and 25 tags; (**c**) messages from the sheep farm with 15 collars and 25 tags; (**d**) messages from the beef cattle farm with 25 collars and 25 tags; and (**f**) messages from the beef cattle farm with 15 collars and 25 tags. A large variation in the number of messages from GPS collars received per day during the duration of the experiment was observed in both farms. In the sheep farm, this indicator was 23.2 messages per day before September 1 st and almost 34.2 messages per day after that date. In the beef cattle farm, the average number of messages per day was 35.2 for the whole period, except for late November and early December, when it was 20.0. The potential number of daily messages was 48, as GPS was activated every 30 min. Animals moved freely around the available grazing area, and the GPS fix-success rate (proportion of scheduled attempts that resulted in a successful location acquisition) as well as the Sigfox fix-success rate (proportion of scheduled messages sent by the Sigfox network), were potentially different in every square meter of the farms. In this case, most of the missing messages were due to the lack of Sigfox coverage, as the GPS fix-success rate was 99.88% in the sheep farm and 97.59% in the beef cattle farm. The average number of daily messages received from collars remain the same despite the number of collars, which is due to the homogeneity of message-sending rates among devices. Nonetheless, the total number of messages from the BLE tags increased as the number of animals fitted with collars was higher, although the average number of tag messages per collar was the same if the entire experiment is considered. The evolution over the experiment of the number of tag messages per collar and the percentage of collar messages with and without tag information is shown in Figure 5.  
The number of tag messages per collar was constant in the beef cattle farm, but a decrease in this indicator was observed in the sheep farm. This effect was due to the displacement of the sheep herd to a different area of the farm, where they grazed in a more dispersed pattern. Figure 6 shows the evolution of the number of collar and tag messages within a day. Figure 5: Evolution of the number of tag messages per GPS collar and the percentage of collar messages with (blue line) and without (orange line) over the experiment (25 collars and 25 tags): (**a**,**c**) sheep farm; and (**b**,**d**) beef cattle farm. As mentioned before, the number of tag messages was directly related to the number of collars. In the sheep farm, the number of tag messages was similar to the number of collar messages with five collars. In the case of beef cattle, a greater number of collars was needed for that. A large difference between the number of tag messages received during daylight and at night was observed in the sheep farm.