# A Low-Cost IoT-Based System to Monitor the Location of a Whole Herd
## Results
### System Validation in Commercial Farms  
During the experiment, a total of 70,275 collar messages were gathered from the sheep farm, as well as 78,791 collar messages from the beef cattle farm. This means 28.29 messages per collar per day in the sheep farm and 31.52 messages per collar per day in the beef cattle farm over a total of 48 attempts. As explained before, each of these messages contains data about the location of the collar and the identification of the tags close to it. Altogether, 208,337 tag messages (83.33 reads per tag per day) were gathered from the sheep farm and 93,645 tag messages (37.46 reads per tag per day) from the beef cattle farm. The KPIs of the system, defined in Section 2.3, are shown in Table 1 as a function of the collar/tag ratio in the herd. In order to choose a collar/tag ratio, different criteria can be considered, e.g., the number of collars needed to track the location of all tags at least once every day, or the number of collars that is necessary to read tags with a temporal resolution equivalent to that of GPS data. For both herds, the number of tags read at least once every day increased when the collar/tag ratio was higher. In the sheep farm, 10 GPS collars were enough to detect all the 25 tags on a daily basis. For cows, 25 collars were needed to reach this figure. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Animal** & **No. GPS** & **No. BLE** & **Average \(\pm\) std.** & **Average \(\pm\) std.** & **Average \(\pm\) std.** & **Average \(\pm\) std. \%** \\
**Type** & **Collars** & **Tags** & **No. Tags Read** & **Minutes between** & **No. Tags Read** & **Messages without** \\  & & & & **per Day** & **Tag Readings** & **per Message** & **Tag Reading** \\ \hline Sheep & 1 & 25 & \(16\pm 2\) & \(477\pm 140\) & \(4\pm 1\) & \(7\pm 5\) \\ Sheep & 2 & 25 & \(20\pm 2\) & \(232\pm 53\) & \(4\pm 1\) & \(7\pm 4\) \\ Sheep & 3 & 25 & \(22\pm 1\) & \(153\pm 30\) & \(4\pm 0\) & \(7\pm 3\) \\ Sheep & 4 & 25 & \(23\pm 1\) & \(114\pm 19\) & \(4\pm 0\) & \(7\pm 2\) \\ Sheep & 5 & 25 & \(23\pm 1\) & \(91\pm 13\) & \(4\pm 0\) & \(7\pm 2\) \\ Sheep & 10 & 25 & \(25\pm 0\) & \(45\pm 4\) & \(4\pm 0\) & \(7\pm 1\) \\ Sheep & 15 & 25 & \(25\pm 0\) & \(30\pm 2\) & \(4\pm 0\) & \(7\pm 1\) \\ Sheep & 20 & 25 & \(25\pm 0\) & \(22\pm 1\) & \(4\pm 0\) & \(7\pm 0\) \\ Sheep & 25 & 25 & \(25\pm 0\) & \(18\pm 0\) & \(4\pm 0\) & \(7\pm 0\) \\ Beef cattle & 1 & 25 & \(9\pm 3\) & \(620\pm 276\) & \(2\pm 0\) & \(17\pm 23\) \\ Beef cattle & 2 & 25 & \(12\pm 2\) & \(415\pm 99\) & \(2\pm 0\) & \(16\pm 15\) \\ Beef cattle & 3 & 25 & \(14\pm 1\) & \(300\pm 55\) & \(2\pm 0\) & \(16\pm 12\) \\ Beef cattle & 4 & 25 & \(16\pm 1\) & \(234\pm 37\) & \(2\pm 0\) & \(16\pm 10\) \\ Beef cattle & 5 & 25 & \(17\pm 1\) & \(192\pm 27\) & \(2\pm 0\) & \(16\pm 9\) \\ Beef cattle & 10 & 25 & \(21\pm 1\) & \(101\pm 9\) & \(2\pm 0\) & \(16\pm 5\) \\ Beef cattle & 15 & 25 & \(23\pm 1\) & \(68\pm 4\) & \(2\pm 0\) & \(16\pm 4\) \\ Beef cattle & 20 & 25 & \(24\pm 0\) & \(51\pm 2\) & \(2\pm 0\) & \(16\pm 2\) \\ Beef cattle & 25 & 25 & \(25\pm 0\) & \(41\pm 0\) & \(2\pm 0\) & \(15\pm 0\) \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Performance of BLE tag messages reception depending on the number of GPS collars. Regarding the average time between consecutive readings of the same BLE tag by any GPS collar, this value decreased rapidly as the number of collars increased. In the sheep farm, 15 collars gave an average time between tag readings of 30 min, which is equivalent to the potential temporal resolution of the messages from GPS collars. As 28.29 messages per collar per day where gathered in the sheep farm, the real average temporal resolution was 50.90 min. In the beef cattle farm, the minimum average time between tag readings was obtained with 25 collars. This value (41 min) was very similar to the real average temporal resolution of GPS collars in this farm (45.69 min). The average number of BLE tags included in each collar message every day is independent of the collar/tag ratio, both for sheep and beef cattle.