This is based on a report by FindMe911.org and it is specifically talking about issues in the Washington DC area based on data obtained from a FOIA (Freedom of Information Act) filing by that group. It is not to mean that this is the condition all over, while I will admit there is a problem with cellular phone location as the GPS signal is seriously disrupted inside of buildings due to the lack of Line of Site.

Yes, this is a problem, but this 90% error rate is based on statistical data from a particular area.