Real-time data about weather plays an important role in the safety of humans. A group of scientists looks into another way of collecting weather information, particularly rainfall, by using wiper speeds of cars on the road as basis for rain intensity.

German scientists at the University of Hanover found out that GPS-equipped vehicles can be used to gauge rainfall by knowing how drivers adjust the speed of the windshield wipers. The project known as "RainCars" lined up several vehicle wiper systems in a laboratory and subjected them to a rain machine that can simulate different rain intensities.

"The experiments have shown that the front visibility is a good indicator for rainfall intensity," said Ehsan Rabiei, lead author of the study.

Using cars cruising on the road can augment the data provided by rain gauges that are positioned around a certain region. The number of rain gauges are often very limited to know the variation of rain intensity in different areas. The team of experts came up with the idea to use cars as moving rain gauges during a meeting with hydrologists and geoinformatics researchers.

"If moving cars could be used to measure rainfall the network density could be improved dramatically," explained Uwe Haberlandt, who acted as project leader of the team.

Aside from subjecting the wiper systems to rain simulation, the researchers also looked into how optical sensors that help automate car wipers work. These sensors make use of infrared to detect the amount of rainfall and with every reading processed, it gives the system an idea of the intensity of the rain and adjusts the wiper speed as necessary.

"The optical sensors measure the rain on the windshield in a more direct and continuous manner so, currently, they would be the better choice for rain sensors in cars... the value of using moving cars to measure rainfall is not about a higher accuracy of rainfall measurements but about a much higher number of measurement points," said Haberlandt.

As the experiment was carried out in a very controlled environment, the researchers are planning to work with a car rental and taxi company to measure rainfall in Hanover.

The study was published in the European Geosciences Union journal.

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