To support increased traffic volumes on already congested air routes, reduced vertical separation minima (RVSM) are being introduced globally, increasing demands on the accuracy of aircraft avionics that report altitude. 

RVSM is focused on reducing vertical separation minimums from 2000 ft to 1000 ft between FL 290 and FL 410. Height Monitoring Units, necessary to verify the Minimum Aircraft System Performance Specification (MASPS) of aircrafts, are found beneath the Upper Air Route (UAR) to ensure that aircraft maintain requested flight levels.

ERA's multilateration technologies have been proven to provide the measuring element of a height monitoring unit.  Due to its extreme accuracy and reliability, MSS by ERA is able to precisely measure aircraft altitudes in a given UAR through its Total vertical error Measurement Unit (TMU). 

In 1998, ERA was selected by EUROCONTROL to deliver Height Measuring Element (HME) within the Reduced Vertical Separation Minimum (RVSM) program. The system was delivered and installed at Linz, Austria, as a part of the HMU system for the EUROCONTROL RVSM program and has been operational since May 2000.