5.6 Monitoring of Height-Keeping Performance Monitoring of Operational Height-keeping Performance 5.6.1 The introduction of RVSM Airspace into the NAT Region has increased the necessity for consistent and accurate reporting by pilots and ATC units, of deviations of 90 m (300 ft) or more from a CFL for any cause. Monitoring of Technical Height-keeping Performance 5.6.2 The NAT RVSM programme, from the outset, required confirmation that the RVSM MASPS were being met and would continue to be met in future years. A technical height-keeping programme was therefore initiated, employing two height monitoring units (HMU) at Strumble (United Kingdom) and Gander (Canada, along with a number of portable GPS monitoring units (GMU). The programme met its initial objectives and continues to produce data as part of an integrated monitoring programme intended to establish RVSM Airspace on a global basis.
