FCC - Indoor Location Accuracy Benchmarks
The April 3, 2020 Nationwide Benchmark is almost due.
The April 3, 2018 benchmark included a barometric pressure requirement too.
Electronic Code of Federal Regulations
"(A) Within 3 years: All CMRS providers shall make uncompensated barometric data available to PSAPs with respect to any 911 call placed from any handset that has the capability to deliver barometric sensor information."