While rain gauges are a good way to measure rainfall, the fact of the matter is that they can’t be placed everywhere, meaning that there will be areas where researchers might not have data on. In a bid to better understand rainfall in general, researchers from the University of Hanover in Germany have launched an initiative called RainCars, which basically takes advantage of cars with built-in GPS to measure rainfall across multiple locations at once.
The idea is that when we drive and it starts to rain, we naturally turn on our wipers. The heavier the rain gets, the faster our wiper speeds gets, and combine this with speed-monitoring sensors, the researchers believe that they will be able to accurately judge the amount of rain in a particular area (or areas). To prove this, they placed a car with a person in it under a sprinkler system. The output rate of the sprinkler system is already known, and all the person in the car has to do is operate their wipers to ensure that they are able to maintain their view through the windscreen.
The researchers discovered that there was a consistent correlation between wiper speed and the amount of water falling, which means that this method could be used as a relatively accurate means of measuring rainfall. There is a caveat which is that different drivers adjust their speeds differently. For example in extremely light rain, like a drizzle, some drivers might not bother with their wipers at all, plus modern cars these days have sensors that adjusts the speed of the wipers for you based on how much water has been detected.
In any case it is a pretty good idea nonetheless and volunteer drivers and taxis have begun to take part in this initiative in the city of Hanover. [Press Release]