Comparison of Mobile Environmental Sensors for Citizen Science Based Climate Monitoring
Authors: Schmidt Felix , Schütze Claudia , Ködel Uta , Schütze Fabian , Liang Christine , Schäfer David , Dietrich Peter 
Published: February 2023

The possibilities of citizen science-based approaches to environmental research and especially climate monitoring have recently expanded. This is among other things due to the availability of diverse measuring equipment at low costs, so that citizen science-based measuring missions can be implemented with a large number of participants. The advantages of high data density and spatial coverage are obvious. These advantages have been exploited for years by platforms such as www.awekas.at or www.weatherunderground.com and many others. With the help of mobile monitoring systems, the spatial coverage can now be extended even further. This means that the variability of climate values such as air temperature and relative humidity in cities can be investigated and more accurate forecasting models can be used.A crucial aspect here is the reliability and comparability of the data collected with different devices. Therefore, we tested and compared within the EU project CityCLIM (www.cityclim.eu) different measurement equipment. Important characteristics of these devices are their low cost, ease of use and data access, data security and protection and the reliability of the measurement data. In the experiments presented here, 4 mobile systems were used: Meteotracker, senseBox, CHEAL5, PAM-AS520. All of these devices can determine air temperature, relative humidity, GPS-location and time and partly also particulate matter. In order to compare these systems, several measurement trips were made in the city of Leipzig in Saxony/Germany at different times of the year.Surprisingly, there are considerable deviations between the devices in all measured values. This starts with the time and the GPS position. Here, there are sometimes shifts of several minutes and several metres. These errors could certainly be corrected with the help of calibration. However, this must also be practicable for the citizen scientist. In general, this example shows that quality control and backup of the data is necessary. In this sense, it is advantageous if there is a possibility to check the data live from the measurement operator or citizen. For this purpose, a direct upload of the data into the online portal/dashboard is very helpful. This direct data transfer also allows a simple and automated evaluation and storage of the large amounts of data.Also the measurements of the air parameters show larger differences. Here, air flow at the sensor during the journey, protection from direct sunlight and the sensors used influence the measurement results. In any case, it is necessary to provide the users with detailed guidelines for the use of the sensors in order to increase the data quality. In summary, it turned out that the mobile measuring systems are suitable for citizen science-based climate observation with some limitations. Through the experiments, clear requirements for the devices could be worked out, which is helpful for the planning of future projects. The investigation of further devices and especially of quality control tools for the data are important next steps.