# Recent Advances in Internet of Things Solutions for Early Warning Systems: A Review
## 7 Landslides
### Reviewed Uses Cases for Landslide EW
\begin{table}
\begin{tabular}{p{113.8 pt} p{113.8 pt} p{113.8 pt}} \hline \hline
**Article** & **Focus and Objectives** & **Results** \\ \hline \multirow{4}{*}{[91]} & \multirow{4}{*}{Development and testing of a threshold-based Landslide EW system that uses a mix of tree topology and star topology to achieve a good trade-off between energy consumption and reliability.} & The system was implemented and it showed better power saving than previous work thanks to the mixed network topology and to the possibility to switch the sensors between a warning mode and a normal mode. LoRa is suggested for long range communication instead of Zigbee if needed. The system requires a geotechnical investigation to determine thresholds. \\ \hline \multirow{4}{*}{[92]} & \multirow{4}{*}{Development of a landslides warning system that uses MEMS tilt sensors and water sensors with a focus on avoiding false alarms through on-site parameters.} & The system was tested and the tilt sensors were successful in monitoring slow ground monitoring for EW; it was observed that tilt variations are not always related to rainfall levels and that local site conditions should be considered besides thresholds based on rainfall. \\ \hline \multirow{4}{*}{[93]} & \multirow{4}{*}{Design of low-cost LoRa sensor nodes to be used alongside more classic ground monitoring sensors. A central station gathers data from the LoRa network and the other sensors and sends it to a Cloud solution called Inform@Risk which processes data to generate alarms.} & The low cost sensors that were developed can allow a wider and more flexible sensor network. A problem of the system is that it might not be able to detect small landslides or issue warnings if there are not significant surface deformation, as it is a shallow system. A larger installation of 130 sensors will soon be tested in Colombia. \\ \hline \multirow{4}{*}{[94]} & \multirow{4}{*}{Camera-based Landslide EW system that uses a simple image processing algorithm that can be implemented on-site to limit images transmission.} & The developed system was able to send a warning to the developed application 5–6 s after the event was detected to alert users. \\ \hline \multirow{4}{*}{[21]} & \multirow{4}{*}{Development of a Machine Learning-based warning system and analyses of Landslide EW architecture to improve their performance and reliability. The predictions are obtained from two algorithms: a nowcasting algorithm and a forecasting one.} & The nowcasting algorithm had a 95\% accuracy in a real scenario and it was a valid solution in case of data acquisition or transmission failures. The forecasting algorithm also implemented allows extra early warning time when the sensor data is available. \\ \hline \multirow{4}{*}{[95]} & \multirow{4}{*}{Proposal of an Edge AI architecture to limit transmissions towards the Cloud and the amount of data to be transferred on the network through processing of sensor data in a local Edge cluster} & Network latency was reduced from 208 ms to 53 ms, and bandwidth consumption from 2.63 Mbps to 249.5 kbps, but data processing lasted up to 12 s. \\ \hline \multirow{4}{*}{[96]} & \multirow{4}{*}{Proposal of an Edge computing early warning solution which allows Edge nodes to run ML models on-site.} & The system increases reliability by making the Edge Nodes predictions independent from the Cloud, but the developed Edge nodes are unable to train models by themselves. \\ \hline \multirow{4}{*}{[97]} & \multirow{4}{*}{Development of 5G Landslide EW system that monitors rainfall, ground fissure, and surface deformation in real time, and generates warnings based on slope deformation, and also provides other communication channels for reliability.} & The implemented communication system allows transmission up to 100 km and it includes redundant channels. The system is able to produce both user interfaces and warnings. \\ \hline \hline \end{tabular}
\end{table} 
Table 7: Reviewed Articles in Landslide EW. into account synchronization and routing for the network.