Original URL: http://www.theregister.co.uk/2013/02/06/signalling_in_the_rain/

Pinging in the rain: Boffins track wet spots using phone masts

Raindrops keep falling on my EDGE

By Bill Ray

Posted in Mobile, 6th February 2013 06:08 GMT

Dutch university boffins working with meteorological experts and, er, T-Mobile have mapped rainfall using records of radio attenuation, producing real-time maps as good as radar and a lot cheaper.

Not that they tried real-time first: as the writeup in the National Academy of Sciences explains, the proof-of-concept uses historical data from September 2011, but that data can be used to create a national rainfall map which accurately traces the recorded precipitation, and without needing the data-gathering or radar equipment normally used to count the raindrops.

It's not the mobile network which is monitored - that is subject to too many variables - but rather the fixed microwave connections used by network base stations to backhaul calls and data connections. Those point-to-point links are attenuated by rain and heavily monitored in case of failure - making them ideal for measuring rainfall.

There are, for example, about 42,000 such links in the UK, most of them in rural areas where fibre-optic cables aren't practical but also providing redundant paths across urban rooftops. That's easily enough data points for accurate rainfall mapping. The video above used only 2,400 such links and currently the UK relies on 18 weather radars dotted around the country.

The problem is getting at the data. While network operators might be happy to share the attenuation, they will likely be less confident about sharing the loading, which might be pertinent. It's telling that the researchers are happy to share the analysed data but can't share the raw numbers as T-Mobile doesn't want that made public.

The UK's largest operator still refuses to say where its base stations are located (making the national SiteFinder map a laughable travesty), and won't be sharing them with the weather forecasters any time soon.

European operators would certainly want paying, which isn't unreasonable but will probably prevent the technique being deployed in Western markets. But there are plenty of countries where rainfall radar is less prevalent, and government shareholdings can be used to pressure the mobile networks into playing along, so the idea has merit.

Certainly it falls into the why-didn't-I-think-of-that category, and the boffins at Wageningen University deserve full credit for proving it can be done. ®