# An Autonomous Thermal Camera System for Monitoring Fumarole Activity
## 4 Discussion  
From looking at the observations in Figure 6, the daily temperature cycles show a high positive correlation. It can be concluded that the radiant temperature recordings of the camera and air temperature of the metastation correspond with the modelled top-soil temperature of the ERA5-Land re-analysis model. However, within each daily cycle, there are deviations of multiple degrees possible.  
The combination of a Raspberry Pi with an Arduino microcontroller is suited for automated observations at specific times of the day or regular intervals: The system sleeps and wakes without problems and comes with low power consumption. The data are momentarily stored on an SD card inside the control unit and on a USB stick outside of the enclosure. The USB sticks can be exchanged for data collection and data are synchronized with those on the internal SD card. This design ensured that data could be read out at any time and did not lead to data loss. However, with growing data volume, not only the time needed to copy data increases but also the time needed to compare between the SD card and the USB stick increased in the synchronization process. We experienced that after a year of data collection (\(\pm 8\) GB), 5 min were insufficient to finish the data comparison, let alone copy the data. In the software update carried out in July 2020, the synchronization process was, therefore, replaced with a simple copy statement only involving the last recorded data.  
In general, the battery condition improved over time, indicating that the design helps to save power in between measurements. In addition, we can conclude that the setup with a marine battery charged by a 100 W solar panel is sufficient for long-term operation in geographic areas close to the equator. However, the Achilles heel of these camera systems is the power supply. Apart from the panel connection error made while setting up the camera system at the gorge, the longer-term data outages could be related to sudden battery breakdowns. A lack of telemetry installed with the system did not allow any early warnings to be sent.  
From practical experience in the field, several possible improvements to the design have come up:  
1. The Raspberry Pi computer in the control unit should be accessible remotely or be made hot-swappable in the field to be able to troubleshoot problems.
2. There should be no cables going through the side of the housing. Instead, these should be interrupted by sealed bayonet connectors. Apart from the severed cables that we encountered inside one of the camera units, USB connectors could loosen over time by pulling cables on the outside.
3. If possible, all camera data, but at least the system health data, should be regularly sent by a wireless connection. This could for example warn of a degrading battery.  
The camera data will be used in the long-term monitoring of fumaroles as surface manifestations of a geothermal system underground. A current debate is whether extracting fluids in geothermal exploitation leads to a decrease in activity in surface manifestations due to fluid extraction, or that dropping pressure leads to increased generation of steam, thereby increasing surface manifestation activity. We plan to investigate this problem with the thermal images provided by our camera units.