# Internet of Things Geosensor Network for Cost-Effective Landslide Early Warning Systems
## 3 Inform@Risk Monitoring System
### Installation  
In general, the installation of the subsurface probes (SN and LCI) can be done with three different techniques, as shown in Figure 5. The first option is direct insertion of the steel casing, using a hydraulic, pneumatic or petrol jackhammer or heavy dynamic probing equipment (DPH). The second option is to pre-drill a borehole of 45-50 mm using a drilling method fitting to the geological conditions and afterwards insert the casing (steel or PVC pipe). The third option allows to directly insert a PVC pipe into the ground using a  
Figure 4: Hardware design of the inclination sensor, the groundwater sensor and the tip and filter section for both the SN and LCI. jackhammer or DPH equipment. This is achieved by placing the steel drilling rod inside the pvc pipe and using a \"lost\" metal tip, which is only loosely attached to the drilling rod and stays in the ground when the drilling is completed and the drilling rod is retracted. To ensure the PVC pipe is is pushed into the ground simultaneously with the drilling rod, a small metal plate with a diameter larger than the pipe is attached to the top of the drilling rod. Which installation technique can be used mainly depends on the subsurface material, the depth and the probe type to be installed. For the SN usually drilling method 1 and for the LCI drilling method 3 will be the best option, as long as no hard rock (stones/blocks or bedrock) is encountered. If this is the case, drilling method 2 will have to be used, which--depending on the required drilling method--makes the installation more complex and costly. This limitation is more significant for the LCI, as it requires higher drilling depths. After the insertion of the casing, the sensors, which are prefractured on the threaded rods (see Figure 4) to lengths of 1 m are installed in the casing and connections are made between each m-segment during the installation. Once all sensors are inserted in the borehole, the LoRa node itself is attached to the top of the casing and the subsurface sensors are connected to the node. Depending on the situation, a protective pipe or some other kind of protection should be added over the node. Figure 5: Installation suggestions for steel casing (blue) and PVC casing (red, green). The installation of these sensors has been tested on a field site in southern Germany (see Section 3.6). Here, also different sensors and attachments were tested in order to find the now final sensor layout. Pictures of this test installation are shown in Figure 6.  
As stated before, the main goal of the system is to increase availability by keeping the costs to a minimum, where possible. The LoRa base module costs about 100 E, including all electronics and power supply. Depending on the attachments, the IN then costs on average 50 E more and the SN and LCI are approximately 100-150 E more expensive because of the casings and the subsurface sensors. The work hours are not taken into account and we are aware that this is also an important cost factor. Yet, it is hard to determine these costs and also, it has been our experience that the local residents are often very willing to help, and they gain more trust to the system if they are engaged in the installation process. If the Inform@Risk PCB is used, the assembly should take about 15-30 min per node, with an additional 30 min for the SN and LCI. The installation on site varies from about 30 min (IN) to 2-4 h for the SN and 4-6 h for the LCI (including drilling), of course depending on the geology and other conditions on site. Comparing these costs with a regular chain inclinometer (starting from approx. 5000 E excl. drilling), our system is more cost effective, although it is clear that the same data quality cannot be achieved. While a chain inclinometer produces absolute deformation measurements with very high accuracy and precision, the SN only provides semi-quantitative data, as we only measure the tilting of the top layer.