Calling 911 from your cell phone in DC? Good luck getting first-responders to find you.

Over a six-month period in 2013, Washington (DC) data show, calls to 911 were easily narrowed down to a general geographic area covered by a single cell tower. But a startling proportion of those calls lacked the latitude-longitude data required by federal regulations for pinpointing people in distress.

The more specific data was missing for as many as 90 percent of such calls over a six-month period in 2013, according to data from the DC government that was provided to the FCC and obtained by the Washington Post. Of the 385,341 wireless calls to 911 made during that time, technological systems were able to provide accurate location data for only 39,805.

Dispatchers in some cases may have been able to get an address from the caller. But in other cases -- for instance, where the caller was unable to speak due to danger or injury -- dispatchers would have had little to go on aside from a search area the size of a few city blocks.

Other data the DC government provided to the Federal Communications Commission -- covering a three-month period in the summer of 2014 and breaking the calls down by wireless carrier -- showed that some carriers did a better job than others at providing the latitude-longitude data. But rates of compliance were still no better than a coin toss, according to the research.