Interesting - carriers need to ..track callers to within 50 meters horizontally and 3 meters vertically

This poses a problem in dense urban areas with high-rise buildings. The private sector companies mentioned in the article who "zipping ahead" of carriers can provide an altitude using things like wifi tracking, but that still needs to be cross-referenced to an actual floor number. (Keep in mind some buildings don't have a 13th floor, etc.) Barometers in phones don't work well indoors either...

So, this may be a case where an FCC regulation is next to impossible to meet, unless someone can figure out how to map altitudes to actual building floor numbers at scale. Seems like that would be pretty labor intensive effort...